• Preheat oven to 350°. Line 24 muffin cups with paper liners.
• Whisk together flour, baking soda, salt and cocoa powder. Set aside.
• Melt the chocolate in the microwave or in a small bowl set over simmering water. Let cool slightly.
• In a large bowl using an electric mixer, beat the butter and sugar at medium speed until well blended. Scrape sides of bowl and beat in the vanilla. Add eggs, 1 at a time, beating just until blended after each addition. Add melted chocolate; beat until blended.
• By hand or with the lowest speed of an electric mixer fitted with a paddle, gradually add flour mixture to chocolate mixture alternately with sour cream, beginning and ending with flour mixture. Beat at low speed (or by hand) until blended. Gradually add hot coffee and stir until smooth.
• Bake at 350° for 20 minutes or until a wooden pick inserted in centers comes out clean. Remove from pans to wire racks, and let cool completely

Sour Cream Chocolate Frosting

• Make sure all your ingredients are at room temperature and that the butter is softened.
• Sift together the powdered sugar and the cocoa powder.
• In a stand mixing bowl, beat the softened butter and half of the sugar mixture just until blended.
• When everything is sticking together, add the vanilla, sour cream and a little of the milk.
• Increase mixer speed and add remaining sugar mixture and a tablespoon of milk. Beat until smooth and creamy, adding more milk as needed.