Preparation Steps

• Line two baking sheets with parchment or silicone mats and set aside. Preheat the oven to 350°F (175°C) when you're ready to bake.
• In a medium bowl whisk together the flour, cocoa powder, cornstarch, baking soda, and salt until evenly combined; set aside.
• In a large mixing bowl, beat the softened butter with both sugars until the mixture is pale and fluffy, about 2–3 minutes using a hand mixer or stand mixer fitted with the paddle.
• Add the egg, vanilla, and white vinegar to the butter-sugar mixture and beat just until incorporated. Stir in the red food coloring and mix until the dough is evenly colored but be careful not to overmix.
• With the mixer on low, gradually add the dry ingredients in two stages, scraping the bowl between additions. Finish folding the last bits by hand with a spatula until there are no streaks of flour.
• Gently fold in the white chocolate chips until distributed throughout the dough.
• Cover the bowl with plastic wrap and chill the dough for at least 1 hour to firm up (overnight is fine and will deepen flavor). Chilled dough is easier to portion and helps prevent excessive spreading.
• Scoop dough by heaping tablespoonfuls (about 1 to 1 1/2 tablespoons each) and place 2 inches apart on the prepared sheets. If the dough warms while scooping, return the tray to the fridge for 10 minutes before baking.
• Bake cookies on the middle rack 9–11 minutes, or until the edges are set and centers still look slightly soft. Bake one sheet at a time for most even results, or rotate sheets halfway if baking two at once.
• Remove from oven and, if desired, press a couple extra white chocolate chips into the warm tops. Let cookies cool on the baking sheet 5 minutes, then transfer to a wire rack to finish cooling.