Brown the butter: melt it in a saucepan over medium heat, stirring frequently, until golden and nutty-smelling, about 5 minutes. Pour into a large bowl and let cool for 10 minutes.

Whisk both sugars into the browned butter. Add the eggs one at a time, whisking well after each, then add the vanilla and whisk until thick and glossy.

In a separate bowl, whisk together the flour, baking soda, and salt. Fold into the wet ingredients until just combined.

Fold in the chocolate chips. Cover the dough and refrigerate for at least 30 minutes (or up to 72 hours for deeper flavor).

Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.

Scoop the dough into balls (about 2 tbsp each) and place 2 inches apart. Sprinkle with flaky sea salt if using.

Bake 10–12 minutes, until the edges are golden but the centers still look slightly underdone. They firm up as they cool.

Cool on the baking sheet for 5 minutes before transferring to a wire rack.