In a heavy 4-qt. saucepan, whisk together eggs, sugar and salt. Gradually add 1 qt. of milk. Cook and stir over low heat until a thermometer reads 160°-170°, about 30-35 minutes.
Pour into a large heat proof bowl; stir in the vanilla, nutmeg and remaining milk. Place bowl in an ice-water bath, stirring frequently until mixture is cool. If mixture separates, process in a blender until smooth. Cover and refrigerate for at least 3 hours.
When ready to serve, beat cream in a large bowl on high until soft peaks form; whisk gently into cooled milk mixture. Pour into a chilled 5-qt. punch bowl. Sprinkle with nutmeg if desired.