Perfectly decorated sugar cookies are not just for cookbooks and magazines. You can make them at home to give your friends and family a tasty and decorative treat for the holidays. To make perfectly decorated cookies you will need two batches of icing: full-strength royal icing and flow, which requires additional water.
Mix 3 cups powdered sugar, 3 tablespoons meringue powder and 6 tablespoons water with a stand mixer on low for 10 to 12 minutes. If using a hand mixer, mix for 14 to 17 minutes until the icing is no longer shiny.
Mix in ½ teaspoon of flavored extract -- almond or lemon, for example – if desired, and food coloring once the icing is done mixing. Make sure to use a gel-based food coloring, such as cake food coloring.
Take two-thirds of the full-strength icing out and place it in a grease-free bowl to make the flow. Add water a few drops at a time until the icing thins out. Mix well as you add water. You will know the flow is ready when you can take a spoon full of icing and drip it into the bowl and by the time you count to 10, all outlines of the icing should have disappeared.
Use full-strength icing first when decorating your cookies. Put the icing in a parchment bag or other pastry bag fitted with a coupler and a #3 tip. Outline your cookie; this will act like a fence or a gate for the flow icing, and will keep it from running over the side of your cookie. You can use a water-dampened paintbrush to smooth out breaks in the icing or to smooth down peaks at end-points of the design.
Add in the flow to the middle of the cookie after the outlines are done. The flow should smooth itself out. Allow it to dry for two to three hours before stacking, or several minutes before adding decorations. If you want two types of flow in a design, add them together before the first layer dries. Add hard candy pieces such as dragees and sanding sugar before the icing dries.