Plan Ahead! The cookie dough needs to chill overnight.

For the Cookies:

• Combine 1/4 cup buttermilk and baking soda in a small bowl. Set aside until step 5.
• In a stand mixer, cream together the butter and sugar.
• Add eggs, salt, vanilla and eggnog. Mix well.
• Add 3 cups of flour, cinnamon, nutmeg, and baking powder. Blend until combined.
• Add the buttermilk/baking soda mixture and the last 3 cups of flour. Mix until the flour is completely incorporated.
• Wrap the cookie dough in plastic wrap and gently press it into a disc. Be sure it is wrapped tightly and refrigerate the dough overnight.
• When you're ready to roll out the dough, preheat the oven to 350 degrees.
• Sprinkle a pastry mat with flour. Divide the dough in half and roll out one-half of the dough, sprinkling flour on top of the dough as needed.
• Cut out the dough in the shapes you'd like. Place the cookies on a nonstick baking mat.
• Bake the cookies at 350 degrees for 9-10 minutes, removing them before they are browned.
• Repeat with remaining dough, rerolling as needed.
• Allow the cookies to cool, then frost them with eggnog frosting and sprinkles, if desired.
• Store in an airtight container.

For the Frosting:

• In a stand mixer bowl, with the mixer on medium speed, whip the butter for 2 minutes until it is almost white in color. 
• Add in the powdered sugar, vanilla, cinnamon, nutmeg and 3 tablespoons of eggnog.
•  Beat on low speed for 3-5 minutes, adding in the last 1-2 tablespoons of eggnog if the buttercream needs to be thinner.

To Decorate the Cookies:

• Use a knife to spread frosting on the cooled cookies, or use a large Wilton cake decorating tip (1M or 2D work great!) to make a pretty swirl.
• To decorate, sprinkle nutmeg on the top of the cookies.
• Store in a single layer in an airtight container.