Begin by separating the Egg Yolks into a medium bow. Whisk and set aside.
In a large saucepan, combine the Cream, Milk, Sugar, and Cocoa Powder. Set over medium-low heat.
Whisk continuously until the Sugar is dissolved and the Cocoa Powder has completely combined, about 4-5 minutes.
Once Sugar is dissolved, temper the eggs by slowly drizzle about 1 cup of the heated cream mixture into the egg yolks. Whisk constantly as you drizzle it in.
Whisk the egg mixture back into the cream mixture in the pot. Add Vanilla.
Return pot to medium-low heat and cook, stirring constantly with a silicone spatula or wooden spoon, until it starts to thicken. It will be done when you are able to coat the spoon and run your finger through the mixture and it doesn't run back into the path of your finger.
Remove from heat and pour through a fine mesh strainer into a medium bowl. This will remove any bits of egg that got "cooked" while they were being tempered by the hot cream mixture.
Cool the mixture to room temperature. Cover and place in the refrigerator to completely cool. This will take 3 - 4 hours. While cooling, occasionally remove from fridge and stir/scrape sides of bowl.
Churn the Ice Cream according to the directions of your ice cream maker's manufacturer. My Cuisenart maker takes between 15-20 minutes.
Serve straight from the ice cream maker, or place in a freezer proof container and freeze for a bit to firm it up. Enjoy!