Combine the milk and cream and heat over a medium high heat. Remove from the heat just before it boils. Add the vanilla extract, cocoa powder and chocolate and whisk well until melted and combined
As the milk is cooling, place the sugar and egg yolks into a clean bowl and whisk vigorously until well combined. The mixture will become paler and increase in size after a couple of minutes
While still whisking vigorously, pour the chocolate mixture slowly into the egg
Return the mixture into the pan on a low medium heat and keep stirring for 3-4 minutes or so until the mixture thickens. To test the thickening, dip a spoon into the custard and run your finger down the back. If it leaves a clean line and holds its shape somewhat then its ready
Remove from the heat, place in a bowl and cool to room temperature. Place it in an ice bath if you wish to speed up this process (See recipe notes) Stir frequently during the cooling process
Once cooled, if using an ice cream maker, follow the user guidelines for best results. Once churned, place in a resealable, freezer-safe container and freeze for 4-6hrs or overnight
If making the recipe manually, cool the mixture as described above in the ice bath and then continue vigorously whisking the mixture for several minutes (depending on whether you're whisking by hand or by electric hand mixer. Once this is done, place in a resealable, freezer-safe container for ½ hour. After ½ hour, remove and stir well using a spatula or a spoon, making sure to scrape down the sides of the container and place back in the freezer. Repeat this process every ½ hour for the next 2 hours. After this, repeat every hour until the desired consistency and smoothness is reached. This repeated process discourages the formation of ice crystals and leaves you with a delicious, smooth ice cream