Melt butter in a saucepan over medium heat, stirring until golden brown and nutty smelling. Cool slightly.
In a large bowl, whisk browned butter, brown sugar, and granulated sugar until smooth. Add eggs and vanilla.
In another bowl, whisk flour, baking soda, and salt. Gradually mix dry ingredients into wet ingredients.
Fold in chocolate chips and chocolate chunks. Chill dough at least 1 hour.
Preheat oven to 350°F and line baking sheets with parchment paper.
Scoop dough onto baking sheet, spacing cookies apart.
Bake 10–12 minutes until edges are golden and centers are slightly soft. Sprinkle with flaky sea salt while warm.