In a medium mixing bowl, whisk together 6 large egg yolks and 1 cup granulated sugar until the mixture is light in color and creamy.
In a medium saucepan over medium heat, combine 1 cup heavy whipping cream, 2 cups whole milk, and ½ teaspoon cinnamon. Heat the mixture, stirring occasionally, until it just begins to simmer.
Next gradually add the hot milk to the egg mixture (1 spoonful at a time) whisking after the addition of each spoonful. You want to gradually add in the heated milk so that you do not scramble the eggs. Follow this process until all the milk has been added to the egg mixture.
Then pour the mixture back into the saucepan on the stove.
Heat on medium low heat and whisk until the mixture is slightly thickened. It will thicken more as it cools.
Remove from the heat and stir in ¼ teaspoon vanilla extract.
Store in the mixture in the refrigerator until chilled and thickened.
Serve topped with fresh whipped cream and additional cinnamon if you prefer.
Enjoy!
Notes
Store the egg nog in an air tight container in the refrigerator for up to 1 week.