Homemade marshmallow frosting is so much easier to make than you think! Similar to marshmallow fluff, this glossy, fluffy frosting can be made with just a few ingredients and is perfect for filling and topping so many cakes and cupcakes.
Bring a small to medium saucepan of water to a boil. (This is not the water called for in the recipe ingredients.)
Place the sugar, corn syrup, salt, ⅓ cup water, and egg whites in a metal or glass bowl that is big enough to sit over the saucepan without the bottom of the bowl touching the water. Do not place the bowl over the pan yet.
Beat the mixture with a handheld electric mixer on medium speed for 1 minute. Place bowl over boiling water.
Beat constantly on high speed with the electric mixer for about 7 minutes, until voluminous and glossy. Beat in vanilla and mix for an additional minute.
Pipe or frost onto cake or cupcakes as desired.
Notes
Use clear vanilla extract for a white frosting. You may use pure vanilla extract, but keep in mind that it will very slightly tint the frosting.