1. Prepare the Milk Mixture

• Measure out the milk and set aside 1/4 cup (60 ml) for later.
• In a medium saucepan, combine the remaining milk, brown sugar, and vanilla extract.
• Heat the mixture over medium heat, stirring occasionally, until it just reaches a boil. Reduce the heat to low once it starts boiling to prevent scorching.

2. Mix the Egg Yolks and Spices

• In a small bowl, whisk together the reserved milk, egg yolks, cinnamon, and a pinch of nutmeg. Ensure the mixture is smooth and the spices are well incorporated.

3. Temper the Egg Mixture

• Slowly drizzle a few tablespoons of the hot milk mixture into the egg yolk mixture, whisking constantly. This step prevents the eggs from curdling.
• Gradually pour the tempered egg mixture into the saucepan with the remaining hot milk, stirring continuously.

4. Cook the Eggnog

• Cook the mixture over low heat for about 10 minutes, stirring constantly with a wooden spoon or heatproof spatula. The mixture should thicken slightly but not boil. It’s ready when it lightly coats the back of a spoon.

5. Add the Rum

• Remove the saucepan from the heat and stir in the dark rum. Adjust the rum quantity to your taste preference, if desired.

6. Cool the Eggnog

• Allow the eggnog to cool completely at room temperature, then transfer it to the refrigerator to chill for at least 1 hour.

7. Whip the Cream

• In a separate bowl, whip the cream to soft peaks. This will be used as a topping for the eggnog.

8. Serve and Garnish

• Pour the chilled eggnog into glasses, leaving room for the whipped cream.
• Top each glass with a dollop of whipped cream, a dusting of cocoa powder, and a cinnamon stick for garnish.