Preparation Steps

• Preheat oven to 350°F and line a cupcake pan with liners.
• Cream the unsalted butter and sugar together until light and fluffy, about 3-4 minutes.
• Add sour cream and vanilla extract and mix until combined.
• Add egg whites in two batches, mixing well after each addition; scrape the bowl as needed.
• In a separate bowl, combine flour, baking powder, nutmeg, and salt.
• Combine eggnog and water in a small cup.
• Add half of the dry ingredients to the batter and mix until combined, then add the eggnog mixture and mix again. Add the remaining dry ingredients and mix well.
• Fill cupcake liners halfway and bake for 15-17 minutes, or until a toothpick inserted comes out with a few crumbs.
• Remove cupcakes from oven and cool in the pan for 2-3 minutes, then transfer to a wire rack to cool completely.
• For the frosting, beat salted butter and shortening until smooth.
• Add 2 cups of powdered sugar and mix until smooth.
• Dissolve instant espresso in hot water and add half to the frosting, mixing until smooth.
• Add the remaining powdered sugar and mix until smooth.
• Add the remaining espresso mixture and eggnog as needed until reaching desired frosting consistency.
• Pipe frosting onto cooled cupcakes and sprinkle with nutmeg if desired.