For the cupcakes

1. Preheat oven to 375°. Remove the butter and eggs from fridge and allow to come to room temperature for 30 minutes, or soften in the microwave for 15 seconds.
2. Combine the butter with the sugar and beat on medium speed until light and fluffy.
3. Add eggs, one at a time, ensuring that each egg is well beaten. Scrape down the sides of the bowl as necessary.
4. In a separate bowl, combine remaining dry ingredients and stir to combine. Add half the flour mixture followed by the rum, and mix just until combined.
5. Pour in remaining dry ingredients, eggnog and sour cream and mix on medium speed until well combined.
6. Using a large cookie scoop, divide the batter evenly, filling each liner 2/3 full.
7. Bake at 375° F for 14-16 minutes. Test cupcakes for doneness by inserting a toothpick into the cupcake. If the toothpick comes out clean, the cupcakes are finished. Allow to cool completely.

For the frosting:

1. Remove butter from fridge and allow to come to room temperature, or soften in the microwave for 15 seconds. Using a stand mixer, beat the butter for several minutes until light and fluffy.
2. Add the powdered sugar one cup at a time and slowly increase speed from low to medium. As the frosting becomes thicker, slowly add eggnog. Beat for several minutes until light and fluffy. Add nutmeg at any point.
3. Pipe onto cooled cupcakes and sprinkle with nutmeg.