Preheat your oven to 325°F. Line an 8x8-inch baking pan with two overlapping sheets of foil, ensuring there’s enough overhang on all sides for easy removal. Lightly grease the foil with cooking spray.

In a bowl, mix the softened cream cheese sour cream, sugar, and flour until well combined with an electric mixer. Set aside while preparing the brownie batter.

Melt the butter in a small saucepan over low heat. Add the chopped chocolate and stir frequently until fully melted and smooth. Remove from heat and let cool slightly.

In a large mixing bowl, whisk together the flour, salt, baking powder, and sugar. Add the eggs and vanilla, stirring until smooth. Pour in the melted chocolate mixture and mix until fully incorporated.

Spread most of the brownie batter into the prepared pan, saving about ⅔ cup for swirling. Gently spread the cream cheese mixture over the brownie base. Drop small spoonfuls of the reserved brownie batter across the top, then use a knife to swirl everything together, creating a marbled effect.

Bake for 35–45 minutes, turning the pan halfway through. The brownies are done when a toothpick inserted into the center comes out with a few moist crumbs. Let them cool in the pan on a wire rack for at least an hour.

Once fully cooled, use the foil overhang to lift the brownies out of the pan. Slice into squares and enjoy! Store leftovers in an airtight container in the refrigerator for up to 5 days.