1. Bring beer and butter to a boil in a small saucepan, over medium-high heat. Stir. 2. Remove from heat and add cocoa powder. Mix. 3. In a large bowl, whisk together flour, sugar, baking soda and salt. 4. Add butter and beer mixture into dry ingredients and mix. 5. Add egg and sour cream and mix. 6. Scoop cupcake batter into lined muffin tin 2/3 the way. 7. Bake 15 minutes at 375. Cool. 8. Use an electric mixer to beat together butter, confectioners’ sugar, peanut butter and milk. 9. Once the ingredients are mixed and smooth, scoop into a piping bag with Wilton tip #12. Frost each cupcake. 10. Sprinkle each frosted cupcake with crushed peanuts.