Preheat pven to 350 degrees. Line cupcake pan with paper liners.
Combine flour, baking powder, baking soda and salt in a bowl.
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugars until light and fluffy. Add eggs and beat well after each addition. Mix in the coffee and combine until completely blended.
While mixer is on low speed, add the cocoa powder and blend completely. Add half the flour mixture and beat until blended. Add the sour cleam and mix until blended. Add the remaining flour mixture and beat just untiil blended.
Fill the cupcake liners 2/3 full and bake for approximately 15-18 minutes, until a toothpick comes out with just a few crumbs.
Allow to cool completely before frosting.