If you're blessed with patience and a freezer --then this polka dot climax is for you. Line bottom of 10-inch angel food cakepan with wax paper. Chill pan. Have ice cream and sherbet frozen hard. Scoop into small balls and refreeze on cooky sheet. Whip whipping cream until stiff. Fold in sugar and vanilla.' Blend in stiffly beaten egg whites. Sprinkle 1/2 cup fine sugar wafer crumbs on bottom of chilled pan. Spread with thin layer of whipped cream mixture. On this place mixed layer of ice cream and sherbet balls. Fill spaces with whipped cream mixture, then sprinkle with more crumbs. Repeat layers until pan is filled. Freeze overnight. Unmold on chilled serving plate. Frost with 1 quart softened ice cream, if desired. Freeze until consistency of thick cream cheese. Sprinkle with additional sugar wafer crumbs. Cut into wedges. Makes 14 to 16 servings.