Preheat your oven to 350°F. Grease or line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth
Add the eggs, one at a time, whisking well after each addition. Stir in the vanilla extract.
Sift in the flour, cocoa powder, and salt. Gently fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.
If using, fold in the chocolate chips for extra richness.Pour the brownie batter into the prepared pan and spread evenly.
In a separate bowl, beat the softened cream cheese and granulated sugar until smooth and creamy.
Add the egg and vanilla extract, mixing until fully combined.
Pour the cheesecake mixture over the brownie batter in the pan. Use a knife or skewer to gently swirl the cheesecake mixture into the brownie batter, creating a marbled effect.
Bake in the preheated oven for 35-40 minutes, or until the edges are set and a toothpick inserted into the center comes out with only a few moist crumbs. Be careful not to overbake—the brownies should remain fudgy!
