In a medium saucepan beat egg yolks and sugar. Slowly beat in 2 cups of the milk.
Cook over medium heat, stirring frequently, until themometer registers 160 degrees or mixture coats back of a metal spoon. Remove from heat; strain into a pitcher.
Stir in remaining milk, bourbon, vanilla and nutmeg. Cover and chill at least 8 hours. When served sprinkle with additional nutmeg.