Easy meatless mushroom burgers with caramelized onions 🍔

Whole mushroom burgers are a great vegetarian alternative to the crumbly veggie patties that fall apart easily. The meaty texture and savory flavor deliver a satisfying burger that hits the spot every time. 

A meatless mushroom burger with lettuce, onion, and tomatoes next to an oyster mushroomPin

Did you know oyster mushrooms can grow to be 25 cm wide? That’s almost 10 inches for the Americans who haven’t adopted the metric system.

Even a mushroom that’s half as wide is still an ideal size for frying and grilling to make a mushroom burger. 

Combined with the fun fact that oyster mushrooms are carnivorous, imagine how exciting mushroom burgers are compared to ordinary beef burgers. 

Let’s learn how to make a mushroom burger in this recipe. 


Why make mushroom burgers

Mushrooms offer a meaty texture with a satisfying mouthfeel that gets pretty close to tasting like a beef patty. They’re super juicy and deliver a savory taste

I love whole mushroom burgers because they avoid the common problems that plague veggie patties. They don’t fall apart or come out with a mushy texture. 

Plus, a mushroom burger is waaay cheaper than eating a fake meat patty from the name brands like Beyond Burger or Impossible Burger. 

NOTE: If you’re looking for a veggie patty made out of ground mushrooms, check out this Macheesmo recipe. If you’re looking for a beef burger with mushrooms, you can make your usual beef burger and top your burger with these garlic butter mushrooms


Types of mushrooms to use

This recipe uses a whole mushroom, the bigger the better. 

Aim to buy a big mushroom that’s at least the size of your brioche bun (I call them burger buns). 

TIP: If possible, buy mushrooms that are 30% bigger than your bun because the mushrooms shrink a lot when you cook them.

My favorite mushroom for mushroom burgers (and what I used for this recipe) is the white oyster mushroom. The mushroom cap can grow to be huge, bigger than my burger bun. 

I grew the mushrooms for this recipe using this white oyster mushroom home-growing kit. You can buy white oyster mushrooms from the fungi vendor at the farmers market

If you can’t find big oyster mushrooms, you can opt for the big portobello mushrooms. Most grocery stores sell these big mushrooms in the produce section.

If you can’t find portobello mushrooms, cook the biggest mushrooms you can buy following the same technique. Then stack the mushroom together (some cheeses can act as a “glue”) and eat carefully.

If you’re using smaller-sized mushrooms, any kind of mushrooms will work, including shiitake, smaller oyster mushrooms like the pink or brown oyster mushrooms, and even chanterelles (beware, chanterelles are pricey). 

NOTE: White button mushrooms and brown button mushrooms are the same as crimini, baby bella, and portobello. The only difference is the color and the size (maturity). They’re all Agaricus bisporus but they go by different marketing names.


How to prepare the mushrooms

The most important thing is to remove the stem (the foot of the mushroom which attaches the cap to the mycelium). I find the stem is the chewiest part. 

The foot of the oysters mushrooms cut off from the mushroom capPin
Remove the foot from the mushroom cap. You can slice up the mushroom foot and cook it in garlic butter with an assortment of over mushrooms in the Garlic Butter Mushroom recipe.

Some people dislike whole mushroom burgers because they find it hard to bite off. In my experience, removing the foot takes care of this problem.

I don’t scrape the gills out of the cap because I don’t feel they interfere with the taste. But if you prefer to scrape the gills off, you can use a spoon to gently remove the gills.

If you choose to wash the mushroom, make sure you pat it dry with a dish towel or paper towel before you cook it.

TIP: Here are tips on how to clean and prepare mushrooms if you’re curious. 


Burger variations

Add your favorite burger mix-ins. The best part about building your burger is the endless possibilities to customize it to your taste buds and what you’ve got in the fridge.

Here are some of my faves (from bottom to the top of the burger).

Bun: brioche, ciabatta, bagel, soft rolls, Hawaiian sweet rolls

Leafy greens: lettuce, mixed greens, baby spinach, pea sprouts, alfalfa sprouts

Cheese: Swiss (and Emmental cheeses), gruyère, provolone, comté, brie (all the varieties of brie), cheddar, fresh mozzarella, smoked mozzarella, halloumi, goat cheese, gouda

Sauces: ketchup, sriracha, garlic aioli, mayonnaise, spicy mayo, mustard, honey mustard, honey dijon mustard, thousand island, BBQ, balsamic vinegar, caesar, buttermilk ranch, pesto 

Toppings: avocado, fried egg (sunny side up), roasted red peppers, sliced tomato, sliced cucumbers, carrot ribbons, grilled pineapple, sliced olives, sliced green onions, bacon, guacamole 

If you’re really ambitious (and a meat eater), you could even add a grilled or fried beef patty to your mushroom burger. 

Make it vegan

Skip the butter and cook the mushroom with your favorite olive oil. Use vegan sauces like ketchup and honey mustard. 

If you’re worried about losing flavor (shouldn’t be a problem with flavorful olive oil), you can marinate the mushrooms with 1 tablespoon of soy sauce and 2 tablespoons of high-quality balsamic vinegar (use the syrupy thick stuff, not the one that smells sharp like white vinegar).

TIP: Marinate the mushrooms in a resealable plastic bag where you can shake the marinade so it fully coats the mushrooms. Leave the marinade on for 10 minutes before cooking.

Make it gluten-free

Use a gluten-free burger bun. Or substitute the bread for a lettuce “bun”.

Here is how I wrapped the lettuce bun. It’s more challenging than using bread but doable, especially with the help of toothpicks to hold the insides together.

A collage of 10 images showing how to fold lettuce to make a "bun" for a mushroom burgerPin

Cooking methods

While I like to pan fry my mushrooms, there are plenty of different ways you can prepare the mushrooms. 

The key to these methods is that you need to melt the butter and baste it onto the mushrooms. Set the mushrooms gill side facing up and add extra butter into the cap.

One alternative is to marinate the mushrooms if you don’t want to baste them with butter. Either way, the key to a juicy mushroom burger is to prevent the mushroom from drying out during cooking.

Oyster mushrooms cooking in butter in a fry panPin
If you’re grilling, broiling, or baking the mushrooms, keep the gills side of the mushroom cap facing up. This increases the chances your mushrooms can capture the butter (or marinade) during cooking.

Grill it: Marinate the mushrooms. Or brush melted butter on the mushrooms. Then grill the mushrooms until cooked. You may want to baste the mushrooms with the marinade or melted butter while they’re grilling.

Broil it: Use your oven broiler or toaster oven on the broil setting. Place the marinated (or butter-brushed) mushrooms on a wire rack with a cookie sheet underneath to catch the marinade that will drip from the mushrooms. Broil for 5 minutes on both sides.

Bake it: Preheat your oven to 400º F/205º C. Bake the marinated (or buttered) mushrooms for 15-20 minutes or until cooked.


Tips for success

  • If using butter, don’t go too hot: Use low to medium heat because butter smokes and burns at high temperatures.
  • Patience: The mushrooms will cook more slowly at medium heat. This means it might take longer to cook the mushrooms in butter. 
  • How to cook this faster: If you’re impatient, you can cook the mushrooms faster using a high-smoking point, neutral oil like canola oil. Set the heat to medium-high and cook the mushrooms with a sprinkling of salt. Then add a few pats of butter once the mushrooms are cooked so you get the delicious butter flavor. 

RELATED: Check out tips on how to cook mushrooms faster.


Easy meatless mushroom burgers with amazing caramelized onions 🍔

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This vegetarian mushroom burger is made with whole mushrooms fried in butter. Mushroom burgers deliver a juicy, satisfying meal thanks to their meaty texture and savory flavor. Enjoy it hot off the stove with your favorite toppings.
Prep Time: 5 minutes
Cook Time: 30 minutes
Total Time: 35 minutes
Course: Main Course
Cuisine: American, Anna&Alex
Keyword: 10 ingredients or less, carbs, comfort, family-friendly, vegetarian
Servings: 4 people
Calories: 393kcal
Author: Anna Rider
Cost: $10

Equipment

  • Knife
  • Chopping Board
  • Frying Pan
  • toothpicks

Ingredients

  • 4 big mushrooms, big oyster or portobello mushrooms work best
  • 4 tablespoons (60 g) butter, salted butter
  • 4 small burger buns

Optional toppings & sauces

  • 1 large Onion
  • ½ teaspoon (2 g) Salt, to taste
  • ½ teaspoon (2 g) Black pepper, to taste
  • 1 small Tomato
  • 4 leaves lettuce, romaine, butter, or iceberg lettuce all work
  • 4 slices cheese, I used gruyère, pick your favorite cheese
  • 2 tablespoons (30 g) mayonnaise

Instructions

Cook the mushrooms

  • Heat the butter in a heavy-bottomed skillet/fry pan on medium heat.
  • After the butter melts, add the mushrooms in a single layer.
  • Once the mushrooms are brown on the underside, flip them over and cook on the raw side. Monitor to make sure the butter is not smoking or burning in the pan. If your heat is too high, turn it down to the medium-low or even low heat setting.
  • Once both sides of the mushrooms are cooked, about 15 minutes, remove them from the heat and set aside.

Caramelize the onions

  • Add the sliced onions to the pan with the remaining butter.
  • Cook the onion rings in the butter. Add the salt and ground black pepper. Toss periodically to ensure even cooking.
  • Once the onions are soft and golden brown, try an onion ring. Don't burn your tongue. If it's caramelized enough to your liking, you can remove the onions from the heat. If they're not ready yet, keep cooking until you're happy with the level of caramelization. Monitor the butter to make sure it's not burning. If it starts to get smoky, add a tablespoon of water.

Toast the buns

  • After you remove the onions from the pan, add the buns to the frying pan to toast them. Put them in cut side touching the pan. This step is optional. You can also toast them in a toaster oven if you have one.
  • Check the underside of the bun. Once the bun is beginning to turn golden, flip the bun over to toast the exterior side.
  • Turn off the heat. Remove the buns from the fry pan if you're worried they might burn. You're ready to assemble the burger.
    A collage of 9 images showing how to cook the mushrooms in butter to make a meatless burgerPin

Assemble the burger

  • Spread your favorite sauce to the top half of the buns.
  • Add the cheese to the bottom half of your buns (the cheese is less likely to fall out if it's on top of the bottom bun instead of the top bun).
  • Add the cooked mushroom on top of the cheese.
  • Add your remaining toppings. In my burgers, I add a slice of tomato on top of each mushroom, a few caramelized onion rings, and a leaf of lettuce.
  • Place the top bun over the lettuce.
  • If the burger isn't holding together, you can poke a toothpick through the top bun and push it down to the bottom bun to hold the insides together. Remember to remove the toothpick when you eat the burger!
  • Enjoy your mushroom burger!
    A collage of 9 images showing how to assemble a mushroom burgerPin

Nutrition

Calories: 393kcal | Carbohydrates: 25g | Protein: 12g | Fat: 28g | Saturated Fat: 14g | Cholesterol: 62mg | Sodium: 827mg | Potassium: 173mg | Fiber: 2g | Sugar: 5g | Vitamin A: 860IU | Vitamin C: 5mg | Calcium: 284mg | Iron: 2mg
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How to scale the recipe

This recipe scales easily because you can easily add as many mushrooms as your frying pan will allow. You can caramelize 2 or 3 onions.

You’ll need more burger buns, sauces, and toppings but those are easy to supply.

TIP: If you’re cooking more than 4 big mushrooms, I would grill or bake them because your grill or oven will be able to cook more mushrooms simultaneously than 1 fry pan. If you don’t want to grill or bake, then you may need to cook the mushrooms in batches to avoid overcrowding them.

Can you make this in advance?

You can cook the mushrooms ahead of time.

However, only assemble the burger when you’re ready to eat. If you assemble the burgers ahead of time, the buns can get soggy from the sauces and vegetables.

How to store leftovers

Store leftover cooked mushrooms in an airtight plastic or glass container. Stash it in the fridge until you’re ready to eat. It should be good for 5 days. 

An oyster mushroom burger with a bite eaten out of itPin
Leftovers? What leftovers? This burger is so tasty, especially with the caramelized onions, that there won’t be leftovers. I had to pry this burger out of Alex’s hands after he took a bite to capture this photo.

Can you freeze it?

Mushroom burgers don’t freeze well because the texture gets soggy once you defrost them. They’re best eaten fresh. You can refrigerated the leftovers for a few days but I wouldn’t freeze them.

How to reheat

You can reheat the cooked mushroom in the microwave. If you don’t have a microwave, you can pan fry it or bake it until it’s steaming hot.


What to eat with mushroom burger

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5-minute spicy garlic cucumber salad
This refreshing garlic cucumber salad is an ideal side dish to balance a heavy main course thanks to its crisp texture and addictive spicy sauce. You'll love it with the original Chinese sauce or the variation sauce if you can't source the exotic ingredients.
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Sautéed Garlic Scapes with Bacon and Shallots
This simple dish of sautéed garlic scapes is packed with flavor. It's a fantastic introduction to garlic scapes if you've never tried them before. The shallots add a sweetness to balance the bacon and garlicky flavor.
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Anna looking down chopping vegetables
About Anna Rider

Hi! I'm Anna, a food writer who documents kitchen experiments on GarlicDelight.com with the help of my physicist and taste-testing husband, Alex. I have an insatiable appetite for noodles 🍜 and believe in "improv cooking".

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