Whisk the yolks and sugar together until pale yellow.
Warm the milk, cream, and nutmeg until it just lightly simmers.
Temper the egg/sugar mixture with the milk/cream mixture.
Return to the saucepan and cook until thickened, stirring slowly and constantly. It should get to 170F.
Remove from heat. Stir in the rum/bourbon. Chill in the refrigerator overnight.
Brown Sugar Bourbon Meringue
Bring sugar and water to boil then simmer for 3 minutes.
Beat whites to soft peaks. With mixer running, slowly pour in the syrup until shiny and stiff peaks form.
Beat in the bourbon.
The meringue works better when using a hand mixer instead of a stand mixer. The stand mixer doesn't always combine the syrup properly and it is more likely to separate.You can also turn this base into eggnog gelato very easily by adding it to your ice cream maker after it has chilled in the refrigerator for 4-8 hours.The base can be made 1 day in advance. But the meringue is best made the same day. You can make the brown sugar simple syrup in advance and keep it in the refrigerator in a sealed container.