Step 1

Place 4 ounces of cream cheese and 2 tablespoons of the unsalted butter in a medium bowl and let sit at room temperature until softened, about 1 hour.

Step 2

Arrange a rack in the middle of the oven and heat the oven to 350°F. Coat an 8x8-inch baking pan with cooking spray. Line with parchment paper or aluminum foil so that it covers the bottom and hangs over two sides. Lightly coat the paper or foil with cooking spray.

Step 3

If using semi-sweet or bittersweet chocolate bars, coarsely chop 10 ounces (no need to chop chocolate chips, you will need 1 1/2 cups plus 2 tablespoons). Transfer 1 cup to a medium microwave-safe bowl and reserve the remaining for topping.

Step 4

Add the remaining 8 tablespoons (1 stick) unsalted butter to the bowl of chocolate. Microwave in 30-second intervals, stirring after each, until almost completely melted and smooth, about 1 minute and 15 seconds. Stir until completely melted and smooth.

Step 5

Add 1 cup of the granulated sugar and whisk to combine. Add 2 of the large eggs and 1 teaspoon of the vanilla extract, and whisk until combined.

Step 6

Place 1 cup plus 2 tablespoons of the all-purpose flour, 2 tablespoons cocoa powder, 1/2 teaspoon kosher salt, and 1/2 teaspoon baking powder in a medium bowl and whisk to combine. Add to the chocolate mixture and stir with a rubber spatula until just combined with no streaks of flour; the batter will be thick.

Step 7

Add the remaining 3 tablespoons granulated sugar, 1 large egg, and 1/2 teaspoon vanilla extract to the cream cheese and butter, and fold with a rubber spatula until a mostly smooth mixture forms. Add the remaining 3 tablespoons all-purpose flour and fold until just combined. It will be smooth with some small lumps.

Step 8

Pour half of the chocolate batter into the baking pan. Pour all of the cream cheese batter over the bottom layer and spread into an even layer. Using a spoon, dollop the remaining chocolate batter evenly onto the cream cheese. The cream cheese should be partially covered with some spots on top. Using a paring knife, swirl the cream cheese into the chocolate batter in a few places but do not over-mix. Sprinkle evenly with the reserved chocolate.

Step 9

Bake until a tester comes out with just a few crumbs, 40 to 42 minutes. Let cool 1 hour. Grasping the excess parchment or foil, lift the brownie slab out of the pan and onto a cutting board. Cut into 16 squares.