Mix all ingredients EXCEPT corn syrup in the bowl of an electric mixer for about 7-10 minutes on low speed, until peaks begin to form. As it is mixing, add the corn syrup. (I add the corn syrup because my meringue powder does not set shiny and the corn syrup adds shine. If you’re meringue powder sets shiny, or if you like a matte finish, you can omit this step.) Thin as needed for outlining or flooding by adding more powdered sugar or water for your need.