Place egg yolks in a medium bowl and lightly beat. Set aside for a moment.
In a large saucepan, heat milk, heavy cream, and brown sugar over medium heat until steaming (do not boil)
Slowly drizzle 1/2 cup hot milk mixture into egg yolks, beating constantly until smooth. Add egg yolk mixture to saucepan and stir occasionally until eggnog is steaming and slightly thickened (do not boil - eggnog will thicken more after chilling)
Remove eggnog from heat and whisk in nutmeg and vanilla. Chill eggnog completely before serving. Enjoy!
Notes
Storing InstructionsStore eggnog in refrigerator up to 1 week.