slightly adapted from Martha Stewart's Yellow Buttermilk Cupcakes
1 1/2 cups cake flour
3/4 cup all-purpose flour
1/4 teaspoon baking soda
1 teaspoon baking powder
1 teaspoon nutmeg
1/2 cup plus 1 Tablespoon butter, room temperature
1 cup plus 3 Tablespoons sugar
1 egg yolk
1 cup eggnog
1 teaspoon vanilla
1 Tablespoon bourbon
Nutmeg Cinnamon Swiss Meringue Buttercream
1. Preheat oven to 350 degrees. Line standard muffin tins with paper liners. Sift together both flours, baking soda, baking powder, salt and nutmeg. In a large measuring cup, add eggnog, vanilla and bourbon.
2. With an electric mixer on medium-high speed, cream butter and sugar until pale and fluffy. Reduce speed to medium. Add whole eggs, one at a time, beating until each is incorporated, scraping down sides of bowl as needed. Add yolk and beat until thoroughly combined. Reduce speed to low. Add flour mixture in three batches, alternating with two additions of eggnog mixture, and beating until combined after each.
3. Divide batter evenly among lined cups, filling each three-quarters full. Bake, rotating tins halfway through, until cupcakes spring back when lightly touched and cake tester inserted in centers comes out clean, about 20 minutes. Transfer tins to wire racks to cool 10 minutes, turn out cupcakes onto racks and let cool completely.