Preheat your oven to 350 degrees. Line a 9x13 inch pan with aluminum foil for easy removal of the bars. Spray with cooking spray and set aside.
In a microwave safe bowl or using a double broiler, melt the 3/4 cup of butter and chopped dark chocolate. Stirring ever 30 seconds being careful not to let the chocolate burn.
Whisk sugar and brown sugar to the melted chocolate mixture. Then add the vanilla and eggs until it it is fully incorporated. Lastly, stir the flour until incorporated.
Pour this mixture into your prepared 9x13 inch pan. Sprinkle with 3/4 cups chocolate chips and set aside.
To make the cheesecake layer, in a stand mixer using the paddle attachment, cream together the cream cheese and softened butter about 2 minutes until fluffy. Mix in the egg, sugar, salt, and vanilla on high for another 2 minutes. Mix in the peanut butter for 2 minutes.
Pour the cream cheese layer over the brownie layer and spread it out so that it is smooth on the top and completely covers the brownie layer. Bake for 35-40 minutes. The top and edges should be slightly golden and the center is set.
Let the bars completely cool and refrigerate for at least an hour or overnight before serving.