In a saucepan over medium heat whisk together cream, half and half, and cocoa powder. Bring to simmer. Stir in chocolate chips until melted. Take off heat and set aside.

In a medium bowl, whisk together sugar and egg yolks until pale yellow and thickened.

Add ½ cup of the cream mixture to egg mixture while continuing to whisk. This will keep your eggs from cooking. Repeat two more times, adding ½ cup cream mixture to egg mixture.

Add the egg mixture to the remaining cream mixture. Put back on stove over medium-low heat, bring to a simmer. Continue to stir until mixture thickens and coats the spoon.

Remove from heat, and pour through a mesh strainer to remove any lumps.

Add vanilla.

Place mixture in ice bath to cool to room temperature. Cover with plastic wrap, making sure to have plastic wrap on the custard to prevent a skin from forming as it chills.

Chill in refrigerator for at least 4 hours, over night is best. Make ice cream per your ice cream maker's directions.