Preheat your oven to 350°F (175°C). Grease a 9x9-inch baking pan or line it with parchment paper for easy removal.
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy. Add in the egg and vanilla extract, mixing until well combined.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Fold in the chocolate chips.
Press half of the cookie dough mixture into the bottom of the prepared baking pan, creating an even layer.
In another bowl, beat the softened cream cheese, granulated sugar, egg, and vanilla extract until smooth and creamy. Spread the cheesecake mixture evenly over the cookie dough layer in the pan.
Dollop the remaining cookie dough on top of the cheesecake layer, spreading it out gently with a spatula. It’s okay if some cheesecake shows through.
Bake in the preheated oven for 30-35 minutes, or until the edges are set and the center is slightly jiggly. Allow to cool completely in the pan before slicing into bars.
For best results, chill the bars in the refrigerator for at least 2 hours before serving to help them set.