Step 1

Preheat oven to 350 degrees. Line 12-cup standard muffin tin with paper liners.

Step 2

Into a medium bowl, sift together cocoa, flour, baking powder, and salt; set aside. In a mixing bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each, then beat in vanilla. With mixer on low speed, add flour mixture in two batches, alternating with sour cream and beginning and ending with flour.

Step 3

Pour batter into cups, filling each 3/4 full. Bake until a toothpick inserted in centers comes out clean, 20 to 25 minutes.

Step 4

Cool in pan 5 minutes; transfer to a wire rack to cool completely, then spread with Easy White Icing using a table knife or small offset spatula. Decorate with sprinkles, if desired.