Preheat oven to 350 degrees. Line an 8x13 or 9x13 baking dish with parchment paper. Spray lightly with non-stick spray.
Melt butter in a sauce pan. Allow the butter to cool for about 15 minutes.
While the butter is cooling, using a hand held mixer, combine the cream cheese topping ingredients until smooth and creamy. Set aside.
To the butter, add the sugar, eggs, and vanilla. Mix until combined well. Add the flour, cocoa powder, baking powder, and salt. Stir well, then fold in the chocolate chips.
Pour the brownie mixture into the baking dish and spread evenly. Top with the cheesecake mixture. Using a spoon, swirl the cheesecake into the brownies.
Bake for 35 to 45 minutes. If you like your brownies more fudgy, cook for 35 and a pick inserted will come out wet. If you want them more done, cook for 45 minutes or until a pick inserted comes out with crumbs.
Let the brownies cool completely in the pan. Carefully lift them out with the parchment paper. Cut into squares. Serve. Refrigerate any leftovers.