How to Make It
Combine first 3 ingredients in a heavy saucepan. Cook over medium heat, stirring frequently, until mixture comes to a boil and sugar dissolves. Continue cooking, stirring frequently, until mixture reaches soft ball stage (240°).
Beat egg whites (at room temperature) until foamy. While beating at medium speed of electric mixer, slowly pour hot syrup in a thin stream over egg whites. Turn mixer to high speed, and continue beating until stiff peaks form and frosting is thick enough to spread. Fold in marshmallows.
Oxmoor House Homestyle Recipes