Preheat oven to 350 degrees. Line a 12-tin cupcake pan with cupcake liners.

Combine cocoa and hot coffee together, stirring until smooth; set aside.

Beat butter with a standing mixer or hand mixer until creamy and fluffy, about 2-3 minutes. Gradually add in sugar, beating 4-5 minutes until it is light and fluffy. Add eggs, 1 at a time, beating just until the yellow disappears.

In a bowl, sift together flour, baking soda, baking powder, salt, and espresso powder.

Alternately mix the coffee/cocoa mixture and flour mixture with the butter batter, beginning and ending with the flour mixture. Do not overmix.

Add in vanilla extract, milk, and sour cream. Mix until just combined.

Divide batter evenly between muffin cups (the batter makes 12-14).

Bake for 17-18 minutes, or until a cake tester comes out clean. Be careful not to overbake, as chocolate cupcakes can get very dry if overbaked.

Allow to cool.

For the frosting, beat butter until light and fluffy. Add in cocoa powder and 2 cups of powdered sugar. Add in heavy cream, a pinch of salt (salt brings out the chocolate flavor).

If the frosting seems too thin, add in the other cup of powdered sugar. If it seems too thick, add in more heavy cream.

Frost cupcakes and enjoy!