Dark Chocolate and Cinnamon Frozen Custard

Based on the recipe found here.

DARK CHOCOLATE AND CINNAMON FROZEN CUSTARD

2 1/2 cups heavy whipping cream
1/2 cup milk
3/4 cup white sugar
2 tablespoons unsweetened dark cocoa powder
1 ounce high-quality dark chocolate (85%), finely chopped
5 egg yolks
1 1/2 tsp. cinnamon, plus more for dusting

Whisk cream, milk, sugar, and cocoa powder in a saucepan over medium heat until the mixture is thoroughly combined and the sugar has dissolved. Bring almost to a simmer and stir in dark chocolate until melted. Whisk egg yolks into the cream mixture and cook until batter is slightly thickened, 1 to 2 minutes. Transfer to a container, cover, and refrigerate until chilled, at least 6 hours.

Stir cinnamon into chilled custard batter and freeze in an ice cream machine following manufacturer's instructions. Sprinkle frozen custard with more cinnamon to serve.