In a large saucepan, heat 2½ cups of the cream over medium-low heat until it begins to simmer around the edges of the pan (do not let it boil).
While the cream is heating, whisk together the eggs, sugar and salt in a large bowl. Ladle out 1 cup of the warm cream mixture and slowly pour it into the egg mixture, whisking constantly. Scrape all of the egg mixture into the saucepan. Continue to cook, stirring constantly with a rubber spatula, being sure to scrape the bottom of the pan as you stir, until the mixture thickens and coats the back of the spatula, a few minutes. The mixture should register 160 to 165 degrees F on an instant-read digital thermometer.
Strain the mixture through a fine-mesh sieve into a clean bowl and allow to cool for 15 minutes, stirring occasionally. Whisk in the rum, whiskey, vanilla extract and 1 teaspoon of the freshly grated nutmeg.
Whip the remaining 1 cup of heavy cream until soft peaks form. Gently fold the whipped cream into the eggnog mixture, making sure the whipped cream is completely incorporated. Serve immediately, topping each serving with a sprinkle of fresh nutmeg. The eggnog can be refrigerated for up to 3 days. Be sure to gently whisk before serving.
This eggnog is definitely strong; if you prefer it less boozy, you can cut back on the alcohol.
If you want to make this completely non-alcoholic, you can simply omit the alcohol.
Rum - I like dark rum in eggnog (Myers's is what I usually buy), but spiced rum would also be fabulous.
Whiskey - I typically use Crown Royal, but use what you like or keep on hand.
Other Alcohol - You can switch up the ratios based on your personal preferences; feel free to swap in others like bourbon, Cognac, scotch, or brandy, as well. And how about a little peppermint schnapps for a festive flavor?!
Make-Ahead - This eggnog can be prepared and refrigerated for up to 3 days (great for preparing for a party!). Be sure to whisk well before serving.
Nutritional values are based on one 4-ounce drink.