Combine the Dry Ingredients: Sift the flour, baking powder, and salt into a bowl. Set aside.

Cream the Butter and Sugar: In a separate bowl, beat the butter and sugar with an electric mixer on medium-high speed for about 3 minutes, until light and fluffy.

Add the Egg and Vanilla: Beat in the egg and vanilla extract until fully incorporated.

Mix the Dough: Reduce the mixer speed to low. Gradually add the flour mixture, alternating with the eggnog, until the dough comes together. Avoid overmixing.

Chill the Dough: Transfer the dough to plastic wrap or parchment paper. Flatten it into a disk, wrap, and refrigerate for at least 30 minutes or overnight, until firm.

Preheat the Oven: Preheat the oven to 325°F. Let the chilled dough sit at room temperature for about 10 minutes, or until it’s easy to roll.

Roll and Cut: Lightly flour your work surface and rolling pin. Roll the dough to an even ¼-inch thickness. Cut into your favorite shapes, placing the cutters close together to minimize scraps.

Arrange the Cookies: Use a spatula to transfer the cutouts to parchment-lined baking sheets, leaving a little space between them.

Bake: Bake small cookies for 10–12 minutes and larger cookies for 12–14 minutes, rotating the baking sheet halfway through. The edges should be lightly golden.

Cool Completely: Let the cookies rest briefly on the baking sheet, then transfer them to a cooling rack.

Prepare the Icing: In a bowl, mix the powdered sugar with 1 tablespoon of milk. Add more milk gradually until the icing reaches a spreadable or drizzle-friendly consistency.

Decorate: Divide the icing into bowls and mix in plant-based food coloring as desired. Decorate the cooled cookies and finish with holiday sprinkles. Let the icing set before storing.