Thoroughly whisk together 1 cup of the cream with the cocoa powder in a medium saucepan. Bring to a boil. Reduce the heat and simmer for 30 seconds, whisking constantly. Remove from the heat and add the chopped chocolate. Stir until smooth. Stir in the remaining cup of cream. Pour the mixture into a laurge bowl, scraping the saucepan as clean as possible.

Using the same saucepan, stir together the milk, sugar and salt. In another bowl, beat the egg yolks. Very slowly, pour 1/2 cup of the warmed milk mixture into the yolks to temper, whisking all the while. Then scrape the yolk mixture back into the saucepan. Over medium heat, cook the egg mixture, stirring constantly with a heatproof spatula. Scrape the bottoms and sides constantly. The mixture will eventually thicken and coat the spatula or a metal spoon. When it does, pour it into bowl with chocolate mixture. Add the vanilla. Whisk until smooth.

Put in the fridge to cool for several hours or overnight. When ready to freeze, pour it into your ice cream maker and freeze according to manufacturers instructions.