What you need:
60g cocoa powder
90g all-purpose flour
1/2 teaspoon baking powder
1/4 teaspoon salt
170g butter, room temp
200g caster sugar
3 large eggs
1 teaspoon vanilla extract
1/2 cup (120ml) sour cream
1) Preheat oven to 180C. Line 12-cup standard muffin tin with paper liners.
2) Into a medium bowl, sift together cocoa, flour, baking powder, and salt; set aside.
3) 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.
4) Pour batter into cups, filling each 3/4 full. Bake until a toothpick inserted in centers comes out clean, 20 to 25 minutes. (I bake them for 20 mins)
Cool in pan 5 minutes; transfer to a wire rack to cool completely.
We enjoy it just like this, no fancy icing or sprinkles or whatever.
Use good quality cocoa powder like VanHouten for best results.
On an un-related note, white square serving dish from Ikea - sweeeeeet.