Preheat oven to 240°C and double line base and sides of a 8 inch springform tin. Set aside.
Place chocolate and 100g of the cream into the Thermomix bowl and melt 5 min/50°C/speed 1. You will need to stop partway through and make sure all the chocolate is beneath the blades.
Add cream cheese, vanilla, salt, sugar, eggs and cocoa, and blend 30 sec/speed 6 Scrape down sides of bowl and repeat if necessary.
Add remaining cream and blend 10 sec/speed 8.
Pour mixture into the prepared tin and tap on the bench to level. Place on a tray and into the oven for 23-25 minutes. The cheesecake will look burnt (duoh) but will still be very jiggly in the middle. Cool to room temperature on a wire rack before wrapping well and transferring to the fridge for at least 12 hours, but longer is better.
Slice into thin wedges and serve. I initially thought I would be serving this with cream, but there is no need.