Beat 3 egg whites with 1/4 tsp white vinegar in a large bowl, using an electric mixer on medium, until foamy. Gradually beat in 5 cups sifted icing sugar until combined. Increase speed to high and beat until icing is thick but still foamy, 3 to 7 min. Stir in 2 to 3 tbsp cold water to thin the icing to desired consistency. It should be thick and smooth.
Originally published in the Today’s Parent January 2016 issue. Photo by Tony Lanz.