In a medium saucepan, combine eggnog, granulated sugar, egg yolks, and cornstarch. Whisk until smooth.

Place over medium heat and whisk continuously for about 7-9 minutes until thickened.

Remove from heat and stir in nutmeg, butter, vanilla extract, and salt until butter is melted.

Strain the mixture through a fine mesh sieve into a clean bowl.

Allow to cool at room temperature for about 10-15 minutes before transferring to a jar.