3/4 stick unsalted butter
4 oz. bittersweet chocolate, coarsely chopped
2 cups all-purpose flour
2/3 cup sugar
1/3 cup unsweetened cocoa powder, sifted
1 tbsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1 1/4 cups buttermilk
1 large egg
1 tsp pure vanilla extract
Centre a rack in the oven and preheat the oven to 375 F. Butter or spray the 12 molds in a regular size muffin pan or fit the molds with paper liners. Place the muffin pan on a baking sheet.
Melt the butter and half the chopped chocolate together in a bowl over a saucepan of simmering water; or do this in the microwave. Remove from the heat.
In a large bowl, whisk together the flour, sugar, cocoa, baking powder, baking soda and salt. In large glass measuring cup or another bowl, whisk the buttermilk, egg and vanilla together until well combined. Pour the liquid ingredients and melted chocolate and butter over the dry ingredients and, with whisk or a rubber spatula, gently but quickly stir to blend. Don't worry about being thorough - a few lumps are better than overmixing the batter. Stir in the remaining chopped chocolate. Divide the batter evenly among the muffin cups.
Bake for about 20 minutes, or until a thin knife inserted into the centre of the muffin comes out clean. Transfer the pan to a rack and cool for 5 minutes before carefully removing each muffin from its mold.
Makes 12 muffins.
Source: Baking From My Home To Yours by Dorie Greenspan, 2006