Here's how I do it:
Day 1. I make I make Mamaw's sugar cookie dough and freeze it overnight (freezing makes it less sticky and much easier to roll it out really thin, tomorrow).
Day 2. The next night, I roll the cookies very, very thinly and wafery and bake them so they're still dough-colored, barely browned (so watch them carefully).
Day 3. I ice the cookies.
Cheryl's Sugar Cookie Icing
3 cups confectioners sugar
3 tablespoons butter (melted and hot)
1 1/2 tsps flavoring extract (vanilla, lemon, orange, etc.)
Food coloring as directed below
Approximately 6-7 tsps of milk
1. In large bowl, sift confectioner's sugar.
2. Mix in very hot melted butter.
3. Stir in the extract.
4. Add food coloring.*
5. Add the milk 1-2 tsps at a time while stirring with a spoon, and mix until it's thick enough to coat a cookie, excess can drip off, but not run off like water!
NOTE: Extract and food coloring will thin the icing, so for every few drops, you need one less tsp. of milk to thin it. Too thin and the icing will turn speckle-y when it cools.
6. Place cookies one at a time upside down in bowl on top of icing. Remove and let excess drip off.
7. Place icing side up on cookie sheet and refrigerate overnight. Once hardened, transfer to air-tight tin.
*If making multiple colors of icing, separate the icing into equal amounts into wide bowls. Add the different food colorings to each bowl and blend until you have the color you want.
The icing isn't only for Christmas. Depending on the holiday, I use different food coloring and flavoring:
Easter = Lemon extract and an assortment of light pastels (just 2-3 drops of yellow/green/blue/red)
Thanksgiving & Halloween = Orange extract and orange food black, browns and purples.
Valentine's day = red and vanilla; I've even made purple hearts for Memorial Day.
Christmas = Vanilla with 3 colors: red, green and white.
To make the colors darker and richer, I mix them like this:
Green = 2 drops of red for every 6 drops of green to make a rich forest green
Red = 2 drops of green for every 6 drops of red makes cranberry
White = The vanilla extract colors it a rich ivory color