1 pound confectioners' sugar
4 tablespoons meringue powder
scant 1/2 cup hot water
1 teaspoon light corn syrup
1 teaspoon clear vanilla extract
gel food color paste, if desired
plastic squeeze bottles
Sift the confectioners' sugar into a medium bowl.
In the bowl of a stand mixer fitted with the paddle attachment, mix the meringue powder and water until foamy. Turn off the mixer, add the sifted sugar. Slowly mix at first to work in the sugar, then increase speed slowly to medium-high. Beat until the mixture is glossy and holds stiff peaks.
Divide the icing into containers for each color you want to use, and press plastic wrap directly on the surface of the icing so it doesn't dry out.
Organize your decorator bags and/or squeeze bottles for your thick outline icing, as well as your flood icing. (Use squeeze bottles for flood icing, pastry bags for outlining.)
Now, start coloring one container of icing, adding a drop or two of gel at a time, until the desired color is reached. Keep in mind that the thinned icing for flooding will have a *slightly* lighter shade. If using this color for outlining, transfer some of the stiff icing to a decorator bag fitted with a small round tip (I use #2). If using this color for outlining, transfer a small amount (about 1/4 of what you think you'll need) to a pastry bag fitted with the tip. Work the icing to the tip, twist the bag at the top, and secure with a twisty tie. Place the bag in a glass that has the bottom covered with a bit of water, so the icing doesn't dry out.
To thin the remaining colored icing, add water a teaspoon at a time until a ribbon of icing falls back on itself after 3 seconds. Transfer thinned icing to squeeze bottle, immediately cover the open tip with a damp paper towel.
Repeat for all containers/colors of icing.
To decorate, work 4-5 cookies at a time, first outlining, then flooding, then adding color. Let dry overnight.
adapted from Bake at 350