This is the best cinnamon ice cream I've ever had. It's creamy, has a strong but not overwhelming cinnamon flavor, and doesn't taste too much like eggs. I halved the recipe because it was too big to fit in my maker.
3 cups heavy cream
1 1/2 cups whole milk
2 vanilla beans, split lengthwise (I used 1 tsp vanilla extract)
1 cup plus 2 tablespoons sugar
6 egg yolks
2 1/2 teaspoon cinnamon
Combine cream and milk in a large sauce pan. Scrape in seeds from vanilla beans; add beans. Bring just to simmer. Whisk sugar and yolks in large bowl to blend. Gradually whisk in hot cream mixture. Return mixture to same saucepan. Stir over medium-low heat until custard thickens and leaves path on back of spoon when finger is drawn across, about 6 min. (do not boil). Strain into large bowl. Whisk in ground cinnamon. (at this point I also added the vanilla extract). Chill until cold, about 3 hours.
Transfer custard to ice cream maker and process according to manufacturer's instructions. Transfer ice cream to a covered container and freeze until firm.