Start by setting up a double boiler. Add about half an inch of water to the bottom pot but do not turn on the heat yet. If you don’t have a double boiler, you can use a heatproof bowl set over a saucepan of simmering water.
In the top part of your double boiler (without heating it yet), crack the 8 eggs. Using an electric hand mixer, beat the eggs until they are light and foamy.
Once the eggs are foamy, add the salt. Gradually incorporate the sugar while beating on low speed. Continue to beat the mixture until it becomes thick and glossy.
Pour 2 cups of room-temperature half-and-half into the egg mixture. Using the electric hand mixer on low, gently combine the ingredients. This helps temper the eggs and prepares the mixture for cooking.
Place the double boiler over medium-low heat. With a whisk, begin whisking the mixture continuously. As the water in the bottom pot begins to form small bubbles (but not boil), reduce the heat to low.
Continuously stir the eggnog mixture to prevent the eggs from curdling. This process requires patience, but it’s essential for achieving the creamy texture eggnog is known for.
Using a food thermometer, check the temperature of the eggnog every few minutes. You will be doing this until the mixture reaches 160°F, which is the point at which the eggs are fully cooked and safe to consume. Avoid overheating, as this can cause the mixture to thicken too much or develop a grainy texture.
Once the mixture reaches 160°F, remove it from the heat immediately. Overcooking at this stage can ruin the smooth consistency.
In a bowl large enough to fit all of the ingredients, pour in the egg and half-and-half mixture. Then stir in the remaining half-and-half, whole milk, vanilla extract, and nutmeg. Mix well to combine all the flavors.
Pour the eggnog into a container with a lid and refrigerate it until thoroughly chilled. This typically takes at least 4 hours, but overnight is even better for allowing the flavors to meld together.
Before serving, give the eggnog a quick stir and pour it into glasses. If desired, garnish with a sprinkle of nutmeg or a cinnamon stick for an extra festive touch!