- 1
Place the sugar in a high-powered blender. Blend until it is super fine, about 1 minute. Weigh out 1 pound (454 grams), then reserve any remainder for another use.
Timer: 1m - 2
Combine the egg whites, cream of tartar, and salt in the bowl of a stand mixer fitted with the paddle attachment. Beat on low speed until smooth, then sill on low speed, stream in the sugar. Once all of the sugar has been incorporated, increase the speed to medium-high and continue to beat until a frosting-like consistency is achieved, about 4 minutes. If you'd like a thinner frosting, beat on a little water (or rum).
Timer: 4m - 3
To color the icing, divide the icing between small bowls. Add gel-based food coloring to each portion of icing and stir well to combine. Start with only a drop or two of each color, adding more as desired.
- 4
Use immediately or store in an airtight container overnight. If you have stored the icing, it may separate overnight; whisk it smooth before using.