01 -
Preheat oven to 325°F (163°C) and line two baking sheets with parchment paper.
02 -
In a medium bowl, whisk together cake flour and kosher salt. Set aside.
03 -
In the bowl of a stand mixer fitted with the paddle attachment, beat 1/3 cup unsalted butter, granulated sugar, and powdered sugar on medium speed for 2-3 minutes until light and fluffy.
04 -
Beat in the egg, vanilla extract, rum extract, and eggnog until fully incorporated.
05 -
Gradually mix the dry ingredients into the butter mixture until a soft dough forms. Do not overmix.
06 -
Portion dough onto prepared baking sheets, spacing evenly. Bake for 12-15 minutes or until edges are set but centers are soft. Cool on baking sheet for 5 minutes, then transfer to a wire rack.
07 -
In a clean stand mixer bowl, beat 1/2 cup unsalted butter until smooth. Add sifted powdered sugar gradually, mixing on low. Add eggnog, rum extract, and salt, and blend until creamy and light.
08 -
Once cookies are fully cooled, spread or pipe buttercream over each cookie. Sprinkle with ground nutmeg before serving.