Whether you have frozen crêpes, refrigerated leftovers, or premade crêpes from the supermarket, it's important to reheat them properly so the taste and texture resemble freshly cooked crêpes. Use a large, thick pan that allows you to evenly reheat the crêpes.
Heat your pan (or wok in my case) on medium heat. Don't get the pan too hot or your cooked crêpe will burn. Add half of the butter to the pan. Your pan should melt the butter but the butter shouldn't sizzle. Place the crêpe directly in the pan.
When the crêpe has softened, flip it over, about 3 minutes. Lift the crêpe up and add the remaining butter under the crêpe. (You can also take the crêpe out of the pan before flipping it so you can safely add the butter if that is more comfortable for you. I'm just lazy.) Push the crêpe around the pan to evenly distribute the butter.
While the underside of the crêpe is heating up, place your crêpe filling on the top of the crêpe, especially if the toppings benefit from melting, such as chocolate. If your filling is fresh fruit or whipped cream, you can fill it later once the crêpe is out of the pan.
Add any additional toppings, such nuts or peanut butter.