Prepare the Red Velvet Brownie Batter: Preheat your oven to 325°F (165°C). In a mixing bowl, combine the melted unsalted butter, granulated sugar, and vanilla extract. Whisk in the eggs one at a time to ensure a smooth texture, then gradually add the flour, cocoa powder, and salt. Finally, mix in the red food coloring until you achieve an even, vibrant hue.
Make the Cheesecake Filling: In another bowl, beat the cream cheese until smooth. Gradually mix in the granulated sugar and corn flour until well combined. Then add the warm double cream and melted white chocolate, followed by the vanilla extract.
Assemble the Brownies: Grease a square baking dish (8x8 inches works best) and pour the red velvet brownie batter in, spreading it evenly. Carefully dollop the cheesecake mixture on top of the brownie layer, gently swirling it with a knife for a marbled effect.
Bake the Brownies: Place the assembled batter in the oven and bake for about 55-60 minutes. To check for doneness, insert a toothpick into the center; it should come out with a few moist crumbs attached, but no wet batter.
Cool and Set: Once baked, remove the brownies from the oven and let them cool in the baking dish for about 20 minutes. Then transfer them to the refrigerator to chill for at least 1 hour before cutting into squares.