1/3 cup butter, softened
1 cup sugar
2 eggs
3/4 cup flour
1/2 cup cocoa
1/4 teaspoon baking powder
1/4 teaspoon salt
1/2 cup milk

Preheat oven to 180°. In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs. Combine the flour, cocoa, baking powder and salt; add to the creamed mixture and mix well.
Mix in the milk.
Fill greased muffin tins with the mixture and bake for 20 minutes