Chocolate Chocolate Chunk Muffins

Center rack in the oven and preheat the oven to 375 degrees F. Butter or spray the muffin pan or fit with paper muffin cups. 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. Remove from the heat.

In a large bowl, whisk together the flour, sugar, cocoa, baking powder, baking soda, and salt. In a large glass measuring cup or another bowl, whisk the buttermilk, egg, and vanilla together until well combined. Pour the liquid ingredients and the melted butter and chocolate over the dry ingredients and with the whisk or a rubber spatula, gently but quickly stir to blend. Do not overmix 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 center of the muffins comes out clean. Transfer the pan to a rack and cool for 5 minutes before carefully removing each muffin from its mold.