Start clean: Prepare your work surface and tools.
Mix dry ingredients: In a bowl, combine cornstarch, cocoa powder and half of the chocolate chips.
Heat liquids: In a saucepan, gently heat the cream, milk, sugar and the other half of chocolate chips over medium heat. Stir continuously until fully melted. Don't let it boil!
Combine: Add the dry mix to the warm liquid and stir until smooth.
Cool: Let the mixture cool completely, then pour into your container.
Freeze: Place in the freezer. Every 30-60 minutes, stir vigorously (or use a hand mixture) to break up the ice crystals and to get air inside the mixture. Repeat 2-3 times for the best texture.