Brown the butter by following the instructions in the linked post. Transfer to a large mixing bowl to cool for 20-30 minutes.

Combine flour, baking soda, and salt in a medium bowl and whisk well.

Mix cooled brown butter with both sugars in a large bowl until combined. It should look thick like wet sand.

Add the egg, milk, and vanilla, mixing until well incorporated and creamy.

Add the flour mixture and fold or mix on low just until combined. Add chocolate chunks and chips, mixing until evenly distributed.

Cover the bowl and refrigerate the dough for 1-4 hours (2 hours is best).

Preheat your oven to 375°F. Line two large cookie sheets with parchment paper.

Use a cookie scoop to portion dough into 14 pieces and roll into balls. Space them 3 inches apart on the baking sheets.

Press extra chocolate chunks on top if desired. Bake for 8-10 minutes until golden on top and soft in the middle.

Let cookies cool on the baking sheet for 2 minutes before transferring to a wire rack. Top with flaky sea salt if desired.