Irish Cocktail Cupcakes

Name: Irish Cocktail Cupcakes
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: European, British
Ingredients: 1 cup Irish stout beer (such as Guinness®); 9 tablespoons unsalted butter, cut into 1-inch pieces; 2 cups dark brown sugar; 0.75 cup unsweetened cocoa powder; 0.75 cup sour cream; 2 eggs; 1 tablespoon vanilla extract; 2 cups all-purpose flour; 2.5 teaspoons baking soda; 1 stick unsalted butter, at room temperature; 2 tablespoons Irish cream liqueur (such as Baileys®), or more to taste; 2 teaspoons Irish whiskey (such as Jameson®), or to taste; 3 cups confectioners' sugar