Prepare an ice bath. In a double boiler, whisk together the milk, whole eggs, egg whites, honey and salt. Heat the mixture, whisking constantly, until it reaches 160 degrees on an instant-read thermometer, about 5 minutes.
Transfer the double-boiler bowl to the ice bath and chill, whisking occasionally. Stir in the yogurt and vanilla. Transfer to a punch bowl and garnish with a sprinkling of nutmeg.