Preheat oven to 160C.
Line a 8x8 inch pan with aluminium foil, then spray with baking spray.
Melt butter and chocolate in a microwave safe bowl for 30 secs.
Stir, then melt at 10 seconds blast if not melted yet.
Mix in sugar, and allow to cool for 5 minutes.
Beat in eggs one at a time.
Change to a wooden spoon or spatula, and mix in flour until batter is glossy.
Reserve 1/4 cup batter, then pour the rest into the prepared pan.
Layer the cream cheese batter on top of the brownie.
Drop dollops of reserved brownie batter on top of the cream cheese mixture.
Use a skewer or back of knife to create swirls.
Bake for 50 to 60 minutes, or until moist, fudgy crumbs adheres to skewer when inserted.
Cool in pan for 5 minutes, then remove from pan to cool on cooling rack.
Allow to cool completely and chill (if you have the time) before slicing into it.