Melt the butter in a non-stick pan over medium-low heat, stirring until it looks brown and has a nutty aroma.

Reduce heat to the lowest setting, add the brown and white sugars, and whisk for 1 minute before removing from heat.

Cool the mixture for 5 minutes until warm but not hot.

Whisk in the egg, egg yolk, vanilla, vinegar, and red food color until smooth and creamy.

Sift the flour, cocoa powder, salt, baking powder, and baking soda into a separate bowl and mix.

Ensure the wet ingredients are not hot, then add dry ingredients to the wet ingredients and fold gently until just combined.

Fold in the chopped chocolate until just combined.

Use a 2 tablespoon cookie scoop to divide the dough into 10 balls and gently form them.

Place the cookie balls on a plate or baking sheet and top with additional chocolate chunks if desired.

Refrigerate for at least 2 hours, ideally overnight.

Preheat oven to 375F and line a large, light colored cookie sheet with parchment paper.

Transfer the cookie balls to the baking sheet, keeping at least 3 inches apart.

Bake for 10-12 minutes depending on desired softness. Bake 1 test cookie first.

Sprinkle with flaky sea salt if desired and let cool for 10-15 minutes before serving.