Prepare the brownie mix as directed on the box. Pour into a greased and parchment-lined 9×9-inch square pan. Bake at 350°F for 15 minutes. It’ll be underbaked which is perfect.
In a bowl, beat the cream cheese, sugar, egg, and vanilla until smooth and creamy.
Spread the cheesecake mixture over the warm, partially baked brownie base. Dollop the raspberry and blueberry jams over the top, then gently swirl with a knife for a red, white, and blue marbled effect.
Return the pan to the oven and bake for another 20–30 minutes, until the cheesecake layer is set but still slightly jiggly in the center.
Let the bars cool to room temp, then refrigerate overnight for clean slices and the best texture.
Once chilled, drizzle with white chocolate and load up on red, white, and blue sprinkles.