Royal icing is hands down my favorite icing for cookie decorating. The egg whites in royal icing make it faster drying than confectioner’s icing, where the liquid content is usually milk or cream, and better for fine detail work, as it’s less prone to spreading. Use this thick formulation as edible glue for adhering sugar dragées and fondant appliqués to cookie tops, or for piecing together large gingerbread structures. For outlining, flooding (aka topcoating), marbling, and other cookie decorating techniques, just thin with water per my consistency adjustments until the desired consistency is reached.