Sift sugar into a bowl of an electric mixer. Add remaining ingredients. Using the paddle attachment, mix on low until sugar is incorporated. Increase speed to medium and beat for 5 minutes. Check for stiff peaks. If needed, increase speed to medium-high and continue beating icing, watching closely for stiff peaks. Once stiff peaks are formed, transfer the icing to bowls and cover with plastic wrap, pressing the wrap onto the icing to prevent crusting. At this point, the icing can be tinted with gel paste food coloring. The icing can also be thinned with water to fill in piped outlines.