113grams (1 stick) butter, melted and slightly cooled (Just melt your butter first thing. It will be cool enough by the time you get to it)
2 teaspoons vanilla extract
1cup chocolate chips or chunks
Preheat your oven to 375 F (190 C) and grease your muffin pan.
Combine flour, cocoa powder, baking powder, baking soda, and salt in a large mixing bowl.
In a smaller bowl, whisk together sugar, melted butter, eggs, buttermilk, and vanilla extract.
Pour wet ingredients over dry ingredients and quickly fold them together with a spatula. Work as quickly and lightly as possible. Try to make sure everything is moistened, but don't worry about getting out all the lumps. You'll end up with tough muffins if you overwork it.
Fold in chocolate chips.
Scoop your batter into your muffin pan. The cups will be nearly full.
Put the pan in the oven and increase the heat to 400 F (200 C). Bake for 18 to 20 minutes or until a toothpick comes out clean.
Turn out your muffins as soon as possible. You can give them a couple minutes to cool off so you don't burn your fingers. If you leave them in the pan to cool, they may have soggy bottoms and you won't get that lovely muffin crust.