In a large, heavy-bottomed saucepan, beat together the eggs and sugar. Stir in the half-and-half. Cook over medium-low heat, stirring constantly, until the mixture is thick enough to coat a metal spoon with a thin film and reaches at least 160&
Just before serving, beat the egg whites in a large bowl with an electric mixer on high speed until stiff peaks form, then fold them into the eggnog. Serve cold in punch cups and sprinkle with nutmeg.
Makes 8 to 10 cups.