How to Make It
Combine powdered sugar, meringue powder, corn syrup, lemon juice, and 4 tablespoons water in a large bowl; stir until completely smooth, adding water, 1 teaspoon at a time, until mixture is pourable but not runny.
If desired, divide icing among separate bowls, and tint with food coloring. Dip tops of cookies in icing, scraping excess off on side of bowl. Place dipped cookies on a wire rack, and let stand until dry and firm, about 1 hour. Alternately, place cookies on a rack set over a rimmed baking sheet and slowly pour icing over cookies, letting excess drip over the sides. Let stand until dry and firm, about 1 hour.