In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.
In a large bowl, beat the butter, brown sugar, and granulated sugar on medium speed with an electric mixer until fluffy and well combined (about 2 minutes).
Beat in the egg, egg yolk, vanilla, vinegar, and food coloring until smooth.
With the mixer on low speed, gradually mix in the dry ingredients just until incorporated. Stir in the white chocolate chips/chunks. (Save a few for topping the cookies if you like.)
Chill the dough for 30-60 minutes. (You can chill before or after scooping.)
Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Bake 9–11 minutes, or until the edges are set and the centers look just slightly underbaked. If desired, press a few extra chocolate chips on top when they come out of the oven.
Cool on the pans for 5 minutes, then transfer to a wire rack to cool completely.
Notes
Natural cocoa powder is recommended rather than Dutch-process. It gives a classic red velvet flavor and keeps the color bright.
Chilling helps the cookies bake up thicker and chewier. A longer chill will give you slightly thicker cookies with a softer center.
Color may vary depending on cocoa and gel coloring. Lighter or deeper shades are both normal.
Storage: Store in an airtight container at room temperature for about 4 days, or freeze baked cookies or dough balls for up to 2 months. Bake dough from frozen, adding 1–2 minutes if needed.