Trim a 1 inch layer of sponge or layer cake 1 inch larger on all sides than 1 quart brick of ice cream. Place on wooden cutting board. (Keep ice cream frozen until ready to use.
Beat 5 egg whites until soft peaks form. Gradually add 2/3 cup sugar, beating until soft peaks form.
Center brick of ice cream on cake layer. Spread meringue over ice cream and cake, sealing all edges of cake. Sprinkle lightly with sugar. Bake in an extremely hot oven 500 degrees until meringue is golden, about 3 minutes. Serve immediately. If desired, assemble Alaska and freeze. Brown just before serving.