1: In a bowl, whisk together the sugar and egg yolks until creamy and pale.
2: In a pot, combine the eggnog, milk, bourbon, vanilla, nutmeg, cinnamon, and salt. Heat gently to steep the spices.
3: Slowly whisk the warm eggnog mixture into the yolks to temper them, then return the mixture to the pot.
4: Cook over medium-low heat, stirring constantly, until the mixture reaches 170°F and thickens slightly.
5: Strain into a container and refrigerate overnight.
6: Churn the chilled mixture in an ice cream machine according to the manufacturer's instructions.
7: Serve immediately for a soft-serve texture or transfer to the freezer until ready to enjoy.
