In a large mixing bowl, beat the softened butter with an electric mixer on medium speed until creamy and smooth, about 2-3 minutes.
Gradually add in the powdered sugar, mixing on low speed until combined. Increase to medium speed and beat until fluffy.
Slowly pour in the eggnog while continuing to mix, ensuring the consistency is smooth.
Add the vanilla extract, ground nutmeg, ground cinnamon, and a pinch of salt to enhance the flavors. Mix until well combined and creamy, about 1-2 minutes.
If the frosting is too thick, you can add a bit more eggnog, a teaspoon at a time, until the desired consistency is reached. If it's too thin, add more powdered sugar as needed.
Once your frosting is ready, use it to frost cupcakes, cakes, or even cookies!
Notes
Adjust consistency with eggnog or powdered sugar as needed.