Step 1

Preheat the oven to 350 degrees F and position a rack in the middle of the oven. Line one 12-cup standard muffin tin or two 24-cup mini-muffin tins with cupcake liners.

Step 2

Combine the butter, cocoa, coffee and 1/3 cup water in a microwave-safe bowl. Cover with plastic wrap and microwave on high until the butter melts, about 1 minute. Whisk to combine.

Step 3

Meanwhile, whisk the flour, sugar, baking powder, baking soda and salt in a large bowl. In a small bowl, beat the sour cream, vanilla and eggs. Whisk the hot cocoa mixture into the dry ingredients. Then stir in the sour cream mixture just to combine; don't overmix.

Step 4

Divide the batter evenly in the prepared muffin tin, filling each cup about three-quarters full. Bake until a toothpick inserted into the center of the cupcakes comes out clean, 18 to 20 minutes for standard cupcakes or 16 to 18 minutes for minis.

Step 5

Cool the cupcakes in the tin on a rack for 10 minutes, then remove from the tin and cool on the rack completely. Frost and decorate as desired.