Preheat the Oven. Preheat your oven to 350°F and line a baking sheet with parchment paper.
Mix the Dry Ingredients. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
Cream the Butter and Sugars. In a large mixing bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy. This takes about 2–3 minutes.
Add the Wet Ingredients. Mix in the egg, vanilla extract, buttermilk (or vinegar), and red food coloring. Stir until well combined.
Combine Wet and Dry Ingredients. Gradually add the dry ingredients to the wet mixture, mixing until just combined. Do not overmix, or the cookies may become dense.
Fold in White Chocolate Chips (Optional). Gently fold in the white chocolate chips if using.
Scoop and Bake. Use a cookie scoop or spoon to drop tablespoon-sized dough balls onto the lined baking sheet, spacing them about 2 inches apart. Bake for 9–11 minutes, or until the edges are set but the centers look slightly soft.
Cool and Enjoy. Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.