- Preheat your oven to 350°F (175°C). 
- Prepare the brownie mix according to the instructions on the box. Press the brownie batter into the bottom of a 9-inch springform pan. Bake for 25-30 minutes or until a toothpick inserted into the centre comes out with a few moist crumbs. Let it cool while preparing the cheesecake filling. 
- In a large bowl, beat the cream cheese and sugar until smooth. Add the vanilla extract and mix until combined. 
- Add the eggs one at a time, mixing well after each addition. 
- Stir in the sour cream and heavy cream until smooth. 
- Pour the cheesecake filling over the cooled brownie crust. 
- Place the springform pan in a larger baking pan. Fill the larger pan with hot water halfway up the sides of the springform pan. This will prevent the cheesecake from cracking. 
- Bake for 55-60 minutes or until the centre is almost set. 
- Turn off the oven and let the cheesecake cool in the oven with the door slightly open for 1 hour. 
- Remove the cheesecake from the oven and refrigerate for at least 4 hours or overnight. 
- Once the cheesecake is chilled and set, remove it from the springform pan. 
- Decorate the top of the cheesecake with chopped cosmic brownies and drizzle with chocolate ganache or fudge sauce. 
- Slice and serve.