In large saucepan, beat together eggs, sugar and salt, if desired. Stir in 2 cups of the milk. Cook over low heat, stirring constantly, until mixture is thick enough to coat a metal spoon and reaches 160 degrees F. Remove from heat. Stir in remaining 2 cups milk and vanilla. Cover and regfigerate until thoroughly chilled, several hours or overnight. Just before serving, pour into bowl or pitcher. Garnish or add stir-ins, if desired. Choose 1 or several of: Chocolate curls, cinnamon sticks, extracts of flavorings, flavored brandy or liqueur, fruit juice or nectar, ground nutmeg, maraschino cherries, orange slices, peppermint sticks or candy canes, plain brandy, run or whiskey, sherbet or ice-cream, whipping cream, whipped. Serve immediately.