In a mixing bowl, whisk together the heavy cream, whole milk, sugar, cocoa powder, and vanilla extract until well combined.

Cover the bowl and refrigerate the mixture for at least 30 minutes.

If you're using chocolate chips, stir them into the mixture after chilling.

Set up your Ninja ice cream maker and pour the chocolate mixture into the bowl.

Turn on your Ninja ice cream maker and churn according to the manufacturer's instructions, usually about 20-30 minutes.

Once it reaches a soft-serve consistency, it’s ready to enjoy. For a firmer texture, transfer it to a container and freeze for an additional 2-4 hours.

Scoop the ice cream into bowls or cones and serve immediately.

If you have any leftovers, store the ice cream in an airtight container in the freezer.