Cook milk, heavy cream, and 1/8 teaspoon ground nutmeg in a saucepan over medium heat, stirring occasionally, 5 to 7 minutes or until steaming (about 150). Reduce heat to low.
Whisk together egg yolks and sugar in a large saucepan until smooth. Cook over low heat, whisking constantly, until mixture reaches at least 160 (about 25 minutes).
Whisk milk mixture into egg mixture. Cool 30 minutes; transfer to a pitcher. Cover and chill 3 to 24 hours.
Pour desired amount of praline or bourbon liqueur into each glass, if desired. Top with eggnog.
