So much better than store-bought, this marshmallow sauce is easier to make than it seems. Add a dollop of the sticky sweet stuff to your next ice cream sundae.
In a small saucepan, combine corn syrup and sugar with 1/4 cup water. Bring to a boil over high heat, and clip on a candy thermometer. Continue to boil, occasionally brushing the sides of the pan with a pastry brush dipped in water to prevent stray granules of sugar from crystallizing.
Meanwhile, in the bowl of an electric mixer fitted with the whisk attachment, whip egg whites until medium peaks form. When the syrup reaches 238 degrees (soft-ball stage), after about 7 minutes, remove from heat. With mixer running at medium speed, very slowly pour the syrup down the side of the bowl of egg whites in a steady stream, beating until syrup is fully incorporated and sauce is shiny and fluffy. Serve.