Preheat the oven to 400F (200C). Grease with butter an 8-inch (20cm) springform pan. Line the pan with 2 sheets of parchment paper, in such a way as to make sure it comes about 2 inches (5m) above the pan. The sheets are lined in a pretty rustic way, creased in some places.
Place chocolate and whipping cream into a heat-proof bowl and melt over a bain-marie. Let it cool slightly.
In a large bowl mix cream cheese with sugar and salt until well combined. With a mixer on medium speed, incorporate eggs, one at a time.
Add vanilla and melted chocolate with cream and mix to incorporate.
With a mixer on low, incorporate flour and cocoa powder.
Pour batter into the prepared pan.
Bake for 40-45 minutes, until deep brown but still jiggly in the center. If it burns too fast while baking, cover with aluminum foil.
Refrigerate the cheesecake right away for at least 4 hours or overnight.
It is best to be served at room temperature. Refrigerate the leftovers, and bring to room temperature before serving.