Make the Graham Cracker Crust: First, crush your graham crackers into fine crumbs. You can use a food processor or put them in a zip-top bag and crush them with a rolling pin.

In a medium bowl, mix together the graham cracker crumbs, sugar, and melted butter until everything is well combined and the mixture resembles wet sand.

Press the mixture firmly into the bottom and up the sides of a 9-inch pie plate. You can use your fingers or the bottom of a measuring cup to get it nice and even. Pre-bake the crust in a preheated oven at 350°F (175°C) for about 8-10 minutes. This step helps it to hold up better. Then, let it cool completely.

Prepare the Eggnog Filling: In a medium saucepan, whisk together the sweetened condensed milk, eggnog, cornstarch, vanilla extract, nutmeg, cinnamon, and salt. Make sure the cornstarch is fully dissolved to prevent lumps.

Whisk in the egg yolks until everything is smooth and well combined.

Cook the Filling: Place the saucepan over medium heat. Cook, stirring constantly, until the mixture thickens and comes to a gentle simmer. It should coat the back of a spoon. This usually takes about 5-8 minutes. Don't let it boil vigorously.

Once the filling has thickened, remove it from the heat. Stir in the butter pieces until they are fully melted and incorporated. This adds richness and shine.

Pour and Chill: Pour the warm eggnog filling into the cooled graham cracker crust. Spread it evenly.

Cover the pie with plastic wrap, pressing it directly onto the surface of the filling to prevent a skin from forming.

Refrigerate the pie for at least 4 hours, or preferably overnight, to allow it to set completely.

Serve: When you're ready to serve, top the pie with whipped cream (if desired) and a sprinkle of nutmeg.