Brown the butter by melting it in a medium saucepan over medium heat until foamy and amber in color, about 5-7 minutes. Let cool for 10 minutes.

In a mixing bowl, whisk together flour, baking soda, and salt. Set aside.

In a large bowl, cream together cooled brown butter, dark brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.

Beat in the eggs one at a time, then stir in vanilla extract.

Gradually add the dry ingredients to the wet mixture, folding gently until just combined.

Fold in chocolate chips and optional dark chocolate chunks.

Chill the dough for at least 30 minutes.

Preheat oven to 350°F (175°C).

Scoop tablespoons of dough onto a lined baking sheet, spacing them apart. Bake for 10-12 minutes until edges are golden brown.

Sprinkle sea salt flakes on top right after removing from the oven. Cool for 5 minutes before transferring to a wire rack.