Heat 200 mL of the heavy cream until just about to boil but not boiling and pour over the chopped 70% dark chocolate. Let sit for three minutes. Stir until the ganache is completely smooth. Set aside while you make the custard.

In the bowl of a stand mixer beat the egg yolks with 100 grams (1/2 cup) of the sugar until very pale and thick ribbons form. Meanwhile whisk the cocoa powder in to the whole milk and the additional 40 mL heavy cream and heat over medium until hot. Once hot (but not boiling), slowly pour into the egg mixture with the mixer running on med-low to temper the egg. Return this custard mixture to the pot, whisk in the ganache mixture, and cook on medium/medium-high until thickened and it reaches at least 175°F. Remove from heat, strain, and then whisk in the teaspoon of salt (or salt to taste, I like mine a bit saltier). Chill this covered in the fridge for at least four hours or over night.

Meanwhile make the blackberry syrup. Puree the blackberries in a blender. Strain (you should have about 1 cup of juice). Place this in a sauce pan with the additional 50 grams of sugar and the vinegar. Cook until reduced by half. Chill in the fridge until ready to use.

When ready to churn, churn the chocolate base in an ice cream maker according to the manufacturers instructions. When the ice cream is done, Stir in the chocolate chips and layer it with the blackberry syrup. Cover tightly with plastic and place in the freezer. Allow to set out and soften for about 10-15 minutes before serving.