Step 1

In the bowl of a stand mixer fitted with a paddle attachment, combine egg white with half the powdered sugar. Mix at low speed until sugar disappears into a paste, then gradually sprinkle in the rest. Increase speed to medium and beat until smooth and light, about 2 minutes. If too stiff, thin icing with a few drops of water. Use immediately; keep covered tightly in plastic to prevent icing from drying in bowl. Royal icing can be kept in an airtight container at room temperature up to 12 hours.

Step 2

For Coloring: To dye royal icing with gel paste (see note), divide into as many bowls as you wish to have colors. Cover each tightly with plastic. Working with 1 bowl at a time, add 1 drop gel paste to a batch of icing, then stir until fully incorporated before adjusting color with more gel. Cover bowls tightly when not in use.