Whisk together half of the cream and cacao powder
Bring to a boil, then reduce heat and boil/simmer for 30 seconds whisking constantly.
Remove from heat and add chopped chocolate and whisk until smooth
Add remaining cream and whisk to combine
Transfer mixture to a large bowl
In a small bowl, whisk together egg yolks
In a saucepan over medium heat, whisk together milk, sugar and sea salt
Once the milk mixture is slightly warm, add half of the warm milk to the beaten egg yolks and whisk to combine
Add the milk/egg mixture back into the saucepan, whisking during the addition
Continue to cook the custard over medium heat, and stir the mixture constantly with a spatula until the it thickens and lightly coats the spatula (it does this when it reaches about 76,7 degrees Celcius)
Pour the thickened custard through a metal strainer into the other ingredients in the bowl, stir until combined
Discard any custard residue left on the strainer
Add the vanilla and stir to combine
Put mixture in the fridge until cold (6+ hours)
Add the mixture to your ice cream churner and follow the directions of your machine to churn the mixture
Transfer the chocolate ice cream to an airtight container and freeze for at least 6 hours