In a medium bowl, combine the egg yolks and whisk to combine. Set aside.
Combine the heavy cream, sugar, vanilla extract, and salt in a sauce pot over low heat. Warm until the mixture just barely begins to simmer. Remove from heat.
Very slowly ladle small quantities of the warm heavy cream mixture into the egg yolks, whisking the egg yolks constantly. Continue to ladle the warm mixture into the yolks until half of the heavy cream mixture has made it into the yolks.
Stir the warm yolk mixture into the remaining heavy cream mixture in the sauce pot.
Return the mixture to low heat and warm for 3-5 minutes (stirring constantly), or until the mixture has thickened slightly.
Remove from heat and stir in the ground nutmeg and cinnamon. Transfer to the refrigerator to cool.
When the mixture is cold, add it to your ice cream maker and prepare according to the machine’s instructions. Garnish with freshly-ground nutmeg if desired.