Icing Recipe for Cookies
3 ¾ cups of confectioners’ sugar
3 large egg whites or an egg binder if you are vegan
½ teaspoon cream of tartar
Pinch of salt
Food coloring, as needed
Step 1: In a bowl combine the sugar, egg whites, cream of tartar and salt. Whisk until stiff and glossy with an electric mixer.
Step 2: To tint the frosting, divide into small bowls. Cover the ones you aren’t using with plastic wrap; the frosting dries out very quickly. Use a rubber spatula to stir in desired food coloring. Though not necessary, it makes life easier if you make two versions of each color — one that is thick to pipe the outline on the cookie, and one that is thinned out slightly with a little water to flood the outline.
Step 3: Transfer frosting to piping bags fitted with very small round tips (sizes 1 to 2 work best). Pipe frosting onto cooled cookies and let set, at least 2 hours.