First brown the butter. Follow the instructions in this post to learn how to brown butter in a 1-quart stainless steel saucepan. It’s easy! Brown specks and a dense golden foam will form at the surface when it is nearly ready. This whole process takes around 8-10 minutes. Immediately pour it into a large mixing bowl, then let it cool for 20-30 minutes until it reaches a temperature just warmer than room temperature.

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

Combine cooled brown butter with both sugars in a large bowl and mix gently with a spatula to combine. It should look thick like thick wet sand.

Add the egg, milk and vanilla and mix it in until well incorporated and creamy-looking.

Add flour mixture and fold it in or mix on low just until mostly combined, then add the chocolate chunks and chips before all of the flour is incorporated and continue mixing until they are evenly distributed.

Cover the bowl and refrigerate the dough for 1-4 hours (in a pinch, you can chill for just 1 hour, but minimum 2 hours is best).

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

Use a 1.35-oz cookie scoop to portion dough into 14 pieces (about 2 oz or 56g each) and roll into smooth balls. Place them onto prepared baking sheets, spacing them 3 inches apart. Press a few extra chunks of chocolate on top if you wish. Do not flatten.

Bake for 8-10 minutes until golden on top, browned around the edges and soft in the middle.

Let cookies cool on baking sheet for 2 minutes before carefully transferring to a wire rack to finish cooling. Top with flaky sea salt if you wish and enjoy!