You need a thermometer to make this, and a bit of patience because you’ll be stirring for a while. Preferably use the kind that clips onto the side of the pot. These may be found in coffee shops and home stores. In a pinch, a candy thermometer will suffice.
Note: If you consistently scrape the bottom of your pan, it will keep the egg from cooking. If you find this has happened and you see a piece of egg, you do not need to throw it away. Simply pour it through a sieve before storage.
Best to store in an empty milk jug with a lid so that you can shake it well before pouring. This needs to be shaken each time before serving, as the spices tend to settle. Use a funnel to pour the egg nog into your empty milk container. You may need someone to help you with this step.
In a large saucepan, beat together eggs and sugar. Stir in the milk.
Cook over a low heat, stirring constantly while touching the bottom of the pan, until it reaches 63°C (145°F) and this temperature is held there for 3 1/2 minutes.
At this stage, the mixture will be thick enough to coat a metal spoon. Remove from heat.
Stir in whipping cream, vanilla, cinnamon, and nutmeg. Cover and refrigerate until thoroughly chilled, several hours or overnight.
Serve garnished with whipped cream and nutmeg. Optionally, add a shot of brandy, bourbon whiskey, or light rum to your glass!