Line a square 8x8 baking pan with parchment paper. Then preheat the oven to 350 F/180 C.
Sift the flour, cocoa powder, and salt into a medium bowl and set aside.
In a mixing bowl, whisk the sugar, eggs, egg yolk, vanilla extract, and red food coloring on medium speed for 2-3 minutes until fluffy and slightly thickened.
With the mixer running on low, add the vinegar and then stream the melted butter into the batter. Mix until just combined.
Gently fold in the sifted dry ingredients with a rubber spatula until just combined.
Pour the brownie batter into the prepared baking pan. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out covered in moist crumbs. (In my kitchen, 27-28 minutes is perfect!)
Let the pan cool completely on a wire rack.
While it's cooling, make the glaze.
Combine the softened cream cheese and powdered sugar. Whisk until smooth and lump free.
Then whisk in the milk and vanilla until the glaze is thick enough to be piped and hold its shape.
Cut the cooled brownies into 16 squares, then pipe the cream cheese glaze over one corner of the brownie.
Finish with sprinkles if desired and enjoy!