Directions

• Preheat the oven to 325°F. Spray a 13-by-9-inch baking pan with cooking spray. Line the pan with parchment paper, leaving 2 inches on the long sides. Spray the parchment paper with cooking spray.
• In a large saucepan over medium-low heat, combine the bittersweet chocolate, 1 cup granulated sugar, brown sugar, and butter, stirring until the chocolate is melted, about 3 minutes. Remove from the heat and whisk in the cocoa powder until smooth. Let cool slightly, about 15 minutes.
• Whisking constantly, add 5 of the eggs, one at a time, mixing until fully incorporated after each addition. Whisk in the red food coloring and 1 tablespoon vanilla. Fold in 1 ¾ cups flour and the salt, stirring until completely smooth. In a small bowl, set aside ½ cup of the brownie batter. Fold the white chocolate chips into the remaining batter.
• Spoon the remaining batter into the prepared pan, using a spatula to spread it into an even layer.
• Meanwhile, in a stand mixer fitted with the paddle attachment or in a large bowl using an electric mixer, beat the cream cheese, the remaining ½ cup granulated sugar, and the remaining 2 teaspoons vanilla at medium speed until fully combined and creamy, 1 to 2 minutes. Scrape the bottom and sides of the bowl. Beat in the sour cream and the remaining egg, mixing until fully combined, 30 seconds to 1 minute. Beat in the remaining 2 tablespoons of flour until just combined.
• Carefully dollop the cheesecake mixture all over the brownie layer; gently spread into a smooth layer. Dollop the reserved ½ cup brownie mixture by the teaspoonful randomly over the top of the cheesecake batter in the pan. Using a toothpick, skewer, or paring knife, swirl the brownie mixture into the cheesecake mixture, being careful not to press too deep to disturb the brownie layer.
• Bake until a wooden pick inserted in the center comes out clean (a few crumbs attached are OK), 50 to 55 minutes. Cool on a wire rack for 1 hour, then refrigerate for an additional hour before cutting and serving.