Pour cold heavy whipping cream into a large mixing bowl. Beat using an electric beater or an egg whisk until stiff peaks form.
Add the sweetened condensed milk and cocoa powder to the bowl and continue beating until fully combined and the color is uniform.
Pour mixture into a loaf pan. Level the top using a spatula.
Cover the loaf pan with plastic wrap making sure the plastic wrap touches the cream.
Place in a freezer and let it freeze for 7 hours. Scoop and enjoy.
Notes
Instead of cocoa powder, you could add 1 cup of chocolate spread or half cup of a chocolate beverage like Ovaltine or Milo. If you choose to add any of these alternate sources of chocolate be use sure to reduce the quantity of sweetened condensed milk so the ice cream doesn't turn out too sweet.