Found these beauties from months ago lurking in one of my photo folders. Love my cute new niece and nephew!
(Follow instructions for cut-out cookies and use a onesie cookie cutter. Allow to cool entirely before frosting.)
Sugar Cookie Frosting
Recipe slightly adapted from Annies Eats
-5 cups powdered sugar
-1/3 cup butter, melted
-2 tsp vanilla extract
-3-5 Tbsp milk (3 1/2- 4 Tbsp is about perfect for me)
Use an electric mixer to whip powdered sugar, butter, and vanilla together until smooth. Add milk 1 Tbsp at a time or until desired consistency is reached. If you over-do it and it is too runny to pipe, let it sit for 15 minutes or so and it will probably firm up a bit. It is best not to add too much milk, because the food coloring will thin your frosting as well and if you want to pipe it you don't want it too thin!
Spoon frosting into separate bowls for each desired color. Tint with food coloring. Spoon into piping bags. Decorate cookies then allow to dry 12-24 hours before stacking. (I usually just leave mine out on cooling racks and when they are close to being dry I lightly drape a clean dishcloth over them to keep them from getting stale. When they are completely dry I store in an airtight container.)
*For onesie cookies I used a medium/large round tip to pipe the frosting on, then garnished with sprinkles. I used a French/closed star tip to make the hearts, and the tutus on the girl cookies (zigzag it tightly across the cookies). I used a small round tip to pipe on the sailboats and snaps.