Combine your egg whites, sifted powdered sugar, and cream of tartar in the bowl of your stand mixer with the whisk attached.
Mix on low to get the ingredients combined then bump up to high for 1-2 minutes. Add in your vanilla extract and whip until it's white. No need to mix for longer than 5 minutes.
Place the royal icing into a bowl or container with a lid. Your THICK royal icing is now ready to be thinned down to the consistency you desire.
Serving: 50g | Calories: 905kcal (45%) | Carbohydrates: 227g (76%) | Protein: 3g (6%) | Sodium: 74mg (3%) | Potassium: 61mg (2%) | Sugar: 221g (246%) | Vitamin A: 310IU (6%) | Iron: 0.7mg (4%)