1Heat oven to 350°F. Place paper baking cup in each of 24 regular-size muffin cups.
2Make and bake cake mix as directed on box for cupcakes, using water, oil and eggs and adding 2 tablespoons of the bourbon. Cool 10 minutes; remove from pans to cooling racks. Cool completely.
3In large bowl, beat butter, cream cheese and mascarpone cheese with electric mixer on low speed until smooth. Add powdered sugar, 1/4 cup at a time, beating until smooth. Add remaining 2 tablespoons bourbon; beat until frosting is smooth and spreadable. Pipe or spread frosting on cupcakes; sprinkle evenly with nutmeg.