01 -
Preheat the oven to 350°F (177°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang on the sides to facilitate easy removal.
02 -
Whisk together all-purpose flour, cocoa powder, baking powder, baking soda, and salt in a medium bowl. Set aside.
03 -
In a large bowl, beat 1 cup softened unsalted butter with granulated sugar and brown sugar until pale and fluffy.
04 -
Add the egg, egg yolk, vanilla extract, red food coloring, and vinegar to the butter mixture. Beat until fully combined and the mixture is evenly tinted.
05 -
Gradually mix the dry ingredients into the wet mixture, blending on low speed just until a cohesive dough forms.
06 -
Press the dough evenly into the prepared pan. Bake for 22 to 25 minutes, or until the top is set and a toothpick inserted in the center comes out clean with moist crumbs.
07 -
Remove from the oven and allow the bars to cool completely in the pan on a wire rack before frosting.
08 -
Beat 8 ounces of softened cream cheese and 1/2 cup softened unsalted butter together until smooth. Gradually add 2 1/2 cups powdered sugar and 1/4 teaspoon salt, beating until thick and creamy. Add up to an additional 1 cup powdered sugar or 1 to 2 tablespoons cream as needed to achieve a spreadable consistency.
09 -
Spread the cream cheese frosting evenly over the cooled cookie base. Use the parchment paper overhang to lift the bars from the pan and cut them into squares.