Sanders-Type Frosting
["1 c. butter, softened", "1 c. white solid shortening", "2 1/2 c. confectioners sugar, divided", "2/3 c. sweetened condensed milk", "2 egg whites", "1 tsp. clear vanilla", "1/4 tsp. salt"]
["In a large bowl, cream butter and shortening until well mixed. Slowly add 2 cups of the confectioners sugar and cream until fluffy.", "Beat in condensed milk until well incorporated and set aside."]
["butter", "white solid shortening", "confectioners sugar", "condensed milk", "egg whites", "clear vanilla", "salt"]