Scald 3 cups milk, reserving 1 cup cold mild for later use. Beat egg yolks and sugar until creamy; add cornstarch, cognac, mashed banana, coconut, and vanilla and remaining cold cup of milk. Stir thoroughly. Beat in scalded milk.
Place mixture in double boiler. Heat, stirring constantly, until mixture begins to thicken. Pour into sherbet glasses. Sprinkle with freshly ground nutmeg if desired. Serve cold with Meringues. 8-10 servings