Preheat your oven to 350°F (175°C) and grease the 9x13 inch baking pan or line it with parchment paper for easy removal.
In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until smooth.
Add in the eggs and vanilla extract, mixing until fully incorporated.
In another bowl, whisk together the flour, baking soda, and salt. Gradually add this mixture to the wet ingredients until just combined.
Fold in the chocolate chips.
Spread half of the cookie dough into the bottom of the prepared baking pan, pressing it down evenly.
In a large mixing bowl, beat the softened cream cheese until smooth.
Add the granulated sugar, eggs, and vanilla extract. Mix until creamy and combined.
Spread the cheesecake mixture over the cookie dough layer in the baking pan.
In another bowl, combine the melted butter and granulated sugar until smooth.
Add in the eggs and vanilla extract, mixing until well combined.
Sift together the flour, cocoa powder, and salt. Gradually fold this mixture into the wet ingredients until just combined.
Pour the brownie batter over the cheesecake layer, spreading it gently to cover the entire surface.
Bake in the preheated oven for 30-40 minutes, or until a toothpick inserted into the center comes out mostly clean.
Allow the bars to cool in the pan on a wire rack, then refrigerate for at least 2 hours before slicing into squares or bars.