Preheat your oven to 350°F (180°C) and line a 9-inch square cake pan with parchment paper.
Melt the unsalted butter and whisk it with granulated and light brown sugars for 2-3 minutes.
Add the eggs, egg yolk, and vanilla extract, mixing gently until just combined.
Incorporate the vegetable oil, red food coloring, and cocoa powder, then fold in the all-purpose flour, cornstarch, salt, and vinegar.
If desired, fold in white chocolate chips until evenly distributed.
Pour the brownie batter into the prepared pan and bake for 20-25 minutes.
Cool completely on a wire rack before frosting.
Beat cream cheese and unsalted butter until smooth, then add powdered sugar and blend until fluffy; add vanilla extract and mix until combined.
Frost the cooled brownies generously and cut into squares.
Enjoy your delightful red velvet brownies!