Preheat oven to 350°F (180°C). Grease and line an 8x8-inch pan with parchment paper, letting the excess extend over the sides of the pan. Set aside.
Place the chopped chocolate in a small heatproof bowl and then set aside.
Add the butter and oil to a small saucepan over medium heat and cook until the mixture just comes to a vigorous simmer, stirring often. Immediately pour the hot butter mixture over the chocolate and let sit for 2 minutes. Whisk until the chocolate is completely smooth and melted, then set aside.
In the bowl of a stand mixer fitted with the whisk attachment, or in a large bowl using an electric hand mixer, whisk together the granulated sugar, brown sugar, and eggs on medium-high until the sugar is *mostly* dissolved, about 5 minutes. Beat in the vanilla, red food coloring, and vinegar until combined.
Add the slightly cooled chocolate mixture and beat until incorporated. Add the flour, cocoa powder, cornstarch, and salt, and use a rubber spatula to gently fold until just combined.
Pour the batter into the prepared baking pan and smooth the top with a spatula. Bake for 20 minutes and then remove the pan from the oven and slam them on a flat surface 2-3 times (this deflates them slightly, giving them a more even texture and encouraging that beautiful crackly top). Return to the oven and bake until a toothpick inserted into the center of the brownies comes out fudgy but the edges look cooked through, about 5-10 additional minutes. The brownies will continue to cook and set as they cool.
Allow brownies to cool completely in the pan. Once cooled, frost with cream cheese frosting.