Spiced Eggnog Oatmeal Cream Pies

Add the flour mixture to the wet ingredients and mix on low until combined. Dough will be very sticky.
Cover dough tightly and chill in the refrigerator for at least 2 hours and up to 3 days. Chilling is imperative for this sticky cookie dough.
Preheat oven to 350F 177C. Line large baking sheets with parchment paper or silicone baking mats. Set aside.
Roll chilled cookie dough into balls about 1 heaping Tablespoon 2425g of dough each and place 3 inches apart on the baking sheets. You should get 24 cookie dough balls.
Bake for 1112 minutes or until very lightly
browned around the edges. The centers will look very soft. Remove from the oven and allow cookies to cool on the baking sheet for 10 minutes before transferring to a wire rack to cool completely. Success Tip If your cookies are spreading too much or unevenly remove them from the oven and use a spoon to lightly push any wonky edges back in towards the center to reshape into circles. You can repeat this trick again as soon as you take them out of the oven after baking.
Make the buttercream filling Using a handheld or stand mixer fitted with a paddle or whisk attachment beat softened butter on high speed until creamy about 1 minute. Add the confectioners sugar and beat on medium speed for 12 minutes. Pour in eggnog and vanilla extract and add a pinch each of cinnamon nutmeg and salt. Beat on high for 23 minutes until fluffy. Pipe or spread some of the cream filling on the bottom side of half of the cookies top with remaining cookies right side up. I used Wilton 199 tip to pipe.
Cover and store leftover cookies at room temperature for up to 1 day. After that store in the refrigerator for up to 1 week to keep the creamy filling fresh.