⅔cupplus 2 tbsp Dutch process unsweetened cocoa powder
6ozsemi sweet or bittersweet chocolatecoarsely chopped
Heat oven to 375ºF. Prepare a 12-cup standard muffin tin with paper liners.
Mix together flour, cocoa powder, baking powder, baking soda and salt. In a separate bowl, mix together the sugar, butter, buttermilk and eggs. Add wet ingredients to the dry ingredients and mix until just combined. Stir in half of the chocolate.
Divide batter between the 12 liners and sprinkle with the remaining chocolate. Bake for 18 to 20 min, or until a toothpick inserted in the center comes out clean.
I used Dutch-process cocoa because it is a bit richer in chocolate flavor and gives the muffins that bakery-style dark chocolate color.