Prepare the base
In a medium saucepan, combine the whole milk, double cream, and half of the sugar. Heat over medium heat until the mixture is hot and just about to simmer.

Whisk the yolks
In a separate bowl, whisk the egg yolks with the remaining sugar until the mixture becomes pale and slightly thickened.

Temper the yolks
Slowly pour a small amount of the hot milk mixture into the egg yolks while whisking constantly to prevent the eggs from scrambling.

Cook the custard
Return the tempered egg mixture to the saucepan. Cook over low to medium heat, stirring continuously until the custard thickens enough to coat the back of a spoon.

Flavor and chill
Remove from heat and stir in the ground cinnamon, vanilla extract, and a pinch of salt. Allow the mixture to cool slightly, then refrigerate for at least 2 hours until fully chilled.

Churn and freeze
Pour the chilled custard into an ice cream maker and churn according to the manufacturer’s instructions. Transfer to a freezer-safe container and freeze for at least 4 hours until firm and scoopable.