Makes 24 cupcakes

For the Guinness Chocolate Cupcakes
•1 cup stout (such as Guinness)
•1 cup (2 sticks) unsalted butter
•3/4 cup unsweetened cocoa powder (preferably Dutch-process)
•2 cups all purpose flour
•2 cups sugar
•1 1/2 teaspoons baking soda
•3/4 teaspoon salt
•2 large eggs
•2/3 cup sour cream

Ganache Filling
•8 ounces bittersweet chocolate
•2/3 cup heavy cream
•2 tablespoons butter, room temperature
•2-3 teaspoons Irish whiskey

Baileys Frosting
•4-5 cups confections sugar
•2 ½ stick unsalted butter, at room temperatue
•6-7 tablespoons Baileys

Special equipment: 1-inch round cookie cutter or an apple corer and a piping bag (though a plastic bag with the corner snipped off will also work)