Preheat the oven to 350 degrees Spray mini muffin tin with non stick baking spray and set aside.
Prepare the sugar cookie dough as directed, or prepare your own favorite homemade version.
Using a cookie scoop or a tablespoon, scoop the cookie dough into the mini muffin tin. Press the dough down into the tin creating a crater in the center. This will help them to bake evenly.
Bake the cookie cups for approximately 9 minutes or until the tops are just starting to turn golden brown. The center will still seem doughy. Press the center down with the spoon again to re-create the crater in the middle, this will make the cup shape. Allow to cool in the pan for about 5 minutes and then remove to continue cooling on a wire rack.
For the frosting place the butter in your mixing bowl. Beat it on high speed for about 30 seconds until the butter is creamy. Spoon in the powdered sugar and mix on a lower speed, slowly pour in the eggnog. Continue to mix until fully combined and nice and creamy!
Add more powdered sugar or eggnog to achieve desired consistency.
Pipe the frosting onto the cooled cookie cups. [url:1]I used a Wilton 2D tip - see it here.[/url]
Serve and enjoy!