Preheat oven to 350 degrees F.
In a stand mixer, add the first 5 ingredients and blend on high until combined well.
In another bowl whisk together the next 5 dry ingredients.
Pour this into the wet ingredients and blend on high until combined.
Gently stir in the chocolate chips.
Grease an 8 by 8 baking dish.
Pour half the brownie batter into the pan. Set aside remaining batter.
Prepare the cheesecake topping using a stand or hand held mixer to blend until smooth.
Pour half the cheesecake topping onto the brownie batter in the pan.
Pour the remaining brownie batter over the the cheesecake topping.
Finish with remaining cheesecake topping.
Use a butterknife to swirl the batter and cheesecake topping together.
Decorate with optional chocolate bar chunks or chips if desired before baking.
Bake 30-35 minutes until toothpick in center comes out clean.
Allow to cool for 15-20 minutes before slicing.