1 teaspoon baking soda 2 cups granulated sugar 3/4 cup butter 1/2 cup buttermilk 1 tablespoon light corn syrup 12 large marshmallows 1 teaspoon vanilla extract
Mix first 5 ingredients together in heavy pot and place over low heat, stirring until completely dissolved. When hot, add marshmallows. Cook until candy thermometer reaches 238 degrees F.
Remove from heat. Add vanilla extract and beat until cloudy. Place pot in pan of hot water to keep at spreading consistency, if desired.
Icing is sufficient for 1 (12 x 9-inch) sheet cake, a 2-layer (9-inch) cake or about 44 cupcakes.
