Homemade Eggnog

Method

1. 1Whisk yolks and sugar. Put the egg yolks and sugar into a medium bowl. Whisk vigorously for 2 to 3 minutes until the mixture is pale yellow, smooth, and thick enough that the whisk leaves a visible trail. This step matters: undissolved sugar will create a gritty texture in the finished eggnog, and yolks that haven't been properly aerated will give a flat, heavy result. Set the bowl aside near the stove within easy reach.
2. 2Heat the milk and cream. Combine the milk, cream, nutmeg, and salt in a medium heavy-bottomed saucepan. Heat over medium heat, stirring occasionally, until the mixture just begins to steam and small bubbles appear at the edges — about 4 to 5 minutes. Do not let it boil. At this point, the liquid should be hot enough to temper the eggs but not so hot that it scrambles them on contact. If it starts bubbling actively, pull it off the heat for 30 seconds before proceeding.
3. 3Temper the eggs. This is the step that prevents scrambled egg in your eggnog. Ladle about 120 ml of the hot milk into the egg yolk mixture in a slow, steady stream, whisking constantly and fast. The goal is to raise the temperature of the eggs gradually. Add another ladleful and whisk again. Once you've added about half the hot milk, the egg mixture is warm enough to combine safely. Pour the egg mixture back into the saucepan with the remaining milk, whisking as you pour.
4. 4Cook to 71°C. Return the saucepan to medium-low heat. Stir constantly with a wooden spoon or heatproof spatula, scraping the bottom and sides of the pan. Cook until the custard thickens enough to coat the back of the spoon — when you run your finger across the back of the spoon, it should leave a clean line. On a thermometer, this is 71 to 74°C (160 to 165°F). Do not let it boil or the eggs will scramble. Remove from heat immediately once it thickens. Strain through a fine-mesh sieve into a clean bowl or pitcher to catch any cooked egg bits.
5. 5Cool, chill, and serve. Stir in the vanilla extract. Let the eggnog cool to room temperature, stirring occasionally to prevent a skin from forming. Then cover and refrigerate for at least 3 hours, preferably overnight — the flavor deepens and the texture thickens considerably as it chills. Before serving, stir well and taste. Add bourbon, rum, or brandy now if using — stir in and taste again. Ladle into glasses over ice or serve straight from the fridge. Grate fresh nutmeg generously over each glass.