Heat the milk, heavy cream, vanilla pod and 180 g sugar in a pan over low heat until the sugar dissolves and bring the mixture to boil.
Remove it from heat and remove the vanilla pod.
Stir the egg yolks in a bowl with the remaining sugar until creamy.
Then stir in the hot milk slowly and set the bowl over a hot water bath and stir until the egg mixture it thickened.
Melt the bittersweet chocolate, mix in the cocoa powder, pour it into the bowl containing the egg yolks.
Pour the cream through a sieve into a stainless steel bowl and let cool completely, stir it frequently.
Freeze the chilled cream in an ice cream maker according to manufacturer's instructions.