Combine the milk and the cream in a 1-quart saucepan on medium heat. While the milk and cream are heating, combine the egg yolk, sugar, and nutmeg in a small bowl.
When the milk mixture begins to simmer, remove from the heat and whisk 1 tablespoon of the milk mixture into the egg/sugar mixture. Continue to add and whisk 1 tablespoon at a time of the milk mixture to the egg mixture until you have added about half of the milk mixture to the egg.Note: What you are doing here is tempering the egg. If you add the egg into the milk/cream mixture right away, the egg would cook and we don't want curdles in the eggnog. By tempering, you are slowly heating the egg to match the temperature of the milk.
Pour the egg mixture into the saucepan. Return the pan back to the stove and reduce the heat to low. Stir or whisk constantly for about 10 minutes or until the mixture reaches the temperature of 160 degrees F. If you don't have a thermometer, cook the eggnog until it begins to thicken slightly, and coats the back of a spoon.Note: Do not allow the mixture to boil, or it will curdle.
Remove the saucepan from the heat and stir in the vanilla.
Pour into a mug, add whisky, rum, bourbon, or brandy to taste, if desired. Refrigerate for at least 30 minutes.
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Notes
Customize Creaminess: To achieve your desired richness in eggnog, experiment with the milk-to-cream ratio while maintaining a total of 1 cup of dairy. Increasing the cream proportion will result in a thicker, creamier texture. This flexibility allows you to tailor the eggnog to your personal preference.
Alcohol's Role in Texture: If you choose to add alcohol like rum, whiskey, or bourbon, it will not only enhance the flavor but also contribute to thickening the eggnog over time in the fridge. This is a great tip for those who prefer a denser consistency and a more complex taste profile.
Scaling Up the Recipe: Looking to make more? This recipe is easily adjustable. Simply double the ingredients to serve more or have extra eggnog on hand. It’s a perfect solution for when you have guests or want to indulge a little more during the holiday season.