In a saucepan, heat 500 ml of full-fat milk until it reaches a simmering point. Do not let it boil.
In a separate bowl, mix 100 grams of sugar, 50 grams of unsweetened cocoa powder, and a pinch of salt.
Gradually add the sugar-cocoa mixture to the simmering milk, stirring continuously to avoid lumps. Cook for 5 minutes on low heat.
In another bowl, whisk 3 egg yolks. Slowly pour a small amount of the hot milk mixture into the egg yolks, whisking continuously to temper the eggs.
Pour the tempered egg mixture back into the saucepan with the remaining milk mixture, and cook on low heat for 8-10 minutes, stirring constantly until the mixture thickens.
Remove the saucepan from heat and add 200 ml of heavy cream and 1 teaspoon of vanilla extract. Mix well.
Allow the mixture to cool to room temperature, then cover and refrigerate for at least 4 hours or overnight.
Pour the chilled mixture into an ice cream maker and churn according to the manufacturer's instructions.
Transfer the churned ice cream to an airtight container and freeze for at least 4 hours or until firm.