Preheat the oven to 325F degrees.
Line a 9x13 inch baking pan with aluminium foil and lightly grease.
In a large bowl mix together the melted butter, sugar, cocoa powder and salt.
Stir in the vanilla extract and eggs.
Gently fold in the flour.
Pour the batter into the prepared pan and bake for 15-20 minutes, or until the top is just set, but still shiny. (It will still be wobbly). Remove from the oven.
As the brownie is baking, make the cheesecake layer.
Beat together the cream cheese and sugar until soft.
Mix in the sour cream, vanilla & cornstarch. Turn off the mixer and scrape down the sides of the bowl.
With the mixer on low, carefully beat in the eggs until just combined.
Spoon the batter overtop of the baked brownie layer, and spread evenly. Be careful, the pan will be hot.
Place in the preheated oven and bake for 30-35 minutes or until the top is just set and has a slight wobble when you nudge the pan.
Turn off the oven, open the oven door and cool in the oven for 30 minutes.
Take the cheesecake out of the oven and cool until it reaches room temperature. Wrap the pan with clingfilm or aluminium foil and chill in the fridge for at least 4 hours or overnight.
Cut into slices and top with pie filling or fresh fruit to serve.
*If using boxed brownie mix, prepare the brownie according to package instructions and then continue with step 6.