Preheat the oven to 325°F (163°C) and arrange six 4-ounce ramekins in a casserole dish.

In a medium saucepan, mix together eggnog, heavy whipping cream, sugar, salt, and nutmeg until it simmers (about 5-7 minutes).

Whisk egg yolks in a bowl until lighter. Slowly add hot cream mixture to temper yolks, then return to saucepan.

Ladle the custard mixture evenly into the ramekins, filling each about three-quarters full.

Pour boiling water into the casserole dish, reaching halfway up the ramekins for an even cooking water bath.

Bake for 20-30 minutes until edges are set and centers jiggly but not sloshy; internal temperature should be 160-170°F.

Cool ramekins on a wire rack for 30 minutes, then chill in the refrigerator for at least 4 hours or overnight.

Sprinkle a thin layer of superfine sugar over the custard in each ramekin.

Caramelize the sugar using a kitchen torch until it turns golden brown; alternatively, broil in the oven for 1-2 minutes.

If needed, chill again for 5-10 minutes in the freezer before serving to maintain the crispy topping.