1 envelope (¼-ounce) unflavored gelatin
2 cups heavy cream
¾ cup commercially prepared eggnog (do not use low-fat)
½ cup sweetened condensed milk (not evaporated milk)
1 teaspoon rum extract
1 teaspoon pure vanilla extract
½ teaspoon nutmeg, plus more for dusting
Whipped cream (homemade or store-bought), for garnish
Place 1 cup of the cream in a medium saucepan and sprinkle the gelatin over it; let the gelatin sit for 5 minutes to soften. Turn heat to low and simmer, stirring, until gelatin is completely dissolved.
Add remaining cream, eggnog and sweetened condensed milk.
Cook over medium heat until steam rises from surface and tiny bubbles form around edges; do not let mixture boil. Remove pan from heat. Stir in extracts and nutmeg. Cover pan and let sit for 15 minutes.
Strain mixture into a 1-quart mold, six 5-ounce molds, or divide among six ramekins, custard cups or dessert dishes. When cool, cover with plastic wrap and chill to set for six hours, or overnight. If unmolding, run a knife around the inside edge of the mold(s) and invert onto a plate or serving dish.
Garnish with additional whipped cream and dust with grated nutmeg. Serve immediately.