Stir together 1 (16-ounce) package powdered sugar, 5 tablespoons milk, and 2 teaspoons vanilla extract just until powdered sugar is moistened and mixture is smooth. Add an additional tablespoon of milk, if needed. Use immediately.

Note: We kept this glaze very thick so that it wouldn't drip all the way down the sides of the Fluted Chocolate-Red Velvet Cakes, but feel free to make it a little thinner if you'd like to drizzle it over other cakes.