Fry the bacon on the stovetop until golden brown and crispy, according to package directions. Do not discard the grease. Instead, pour it into a heat-proof container, let it cool, and save it for the frosting. Let the bacon drain on a paper towel, then chop it into bits and set aside.
Heat the oven to 350 degrees F. Line mini cupcake tins with paper liners.
In the bowl of an electric mixer, beat egg and sour cream.
In another bowl, combine flour, sugar, baking soda, and salt. Set aside.
Combine beer and butter in a saucepan and heat until butter melts.
Remove from heat and whisk in cocoa powder to the butter mixture. With the mixer running, slowly pour the hot cocoa/butter mixture into the mixer bowl. Beat until incorporated.
Slowly add the dry ingredients to the wet ingredients and beat until incorporated.
Fold in ½ of the chopped bacon into the batter.
Fill cupcake tins ⅔ full. A squeeze bottle or small scoop is a great way to portion while keeping the mess to a minimum.
Bake for 10-12 minutes, or until the cupcakes spring back to the touch and a cake tester comes out clean. Let cupcakes cool completely on a wire rack before frosting.