Combine all ingredients for the brownie/crust. Mix just until combined and damp. Do NOT overmix or it will be tough. Pour into bottom of a greased 13x9 pan
Combine all ingredients for the cheesecake EXCEPT the blackberry jam. Pour in dollops on top of the brownie/crust and gently spread to cover.
Drop jam by dollops over the cheesecake then swirl it in. Cover pan with foil.
Bake for 35-45 minutes. To check for doneness the cheesecake should be slightly cracked on top and a knife when inserted should come out clean(bear in mind there are chocolate pieces and jam that may deceive you!)
Let cool slightly before digging in. This is pure deliciousness HOT or COLD but try to resist the urge to eat it too soon because you might just burn yourself :P