Decrease the temperature of the oven to 150°C.
In a pot make a dark chocolate pudding with semi-fat milk according to the instructions on the packaging. Let the pudding cool completely.
Mix the mascarpone on high speed until creamy. Add melted chocolate, cool dark chocolate pudding, and mix on high speed until they are fully combined.
Add cornstarch, and regular white sugar, and mix on medium-high speed again. Add eggs, one at a time, and mix on low speed until they are fully combined.
Prepare a baking tray with boiling water. Put a baking tray on the bottom of the oven.
Pour the cheesecake mixture into a cake tin and bake for 50-60 minutes. The cheesecake is well baked when it's jiggly like jelly. Open the door on the oven and let the cheesecake in the oven for another hour.
Take the cheesecake out of the oven and let cool completely. When it's cool, put it in the fridge for at least an hour.