Preparation

• First brown the butter. Follow the instructions in this post here to learn how to brown butter in a 1-quart stainless steel saucepan. It should take 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.
• Add the egg, milk and vanilla and mix until creamy-looking.
• Add flour mixture and fold it in or mix on low until mostly combined, then add the chocolate chunks and chips.
• Cover the bowl and refrigerate the dough for 1-4 hours.
• 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 and roll into smooth balls. Place them on the baking sheets, spacing 3 inches apart.
• Bake for 8-10 minutes until golden on top, browned around the edges 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.