Cook butter in a medium saucepan over medium heat, stirring often, until it foams, then browns, 5–8 minutes. Scrape into a large bowl and let cool slightly., about 10 minutes (an instant-read thermometer should register 125°).

Meanwhile, whisk flour, baking soda, and salt in a medium bowl.

Add brown sugar and granulated sugar to browned butter. Mix until just combined.

Add egg yolk, egg and vanilla and mix until combined.

Add dry ingredients and beat just to combine, then add chocolate chips with a wooden spoon or rubber spatula.

Let dough sit at room temperature at least 30 minutes to allow flour to hydrate.

Place a rack in middle of oven; preheat to 350°. Using a 1-oz. ice cream scoop, portion out balls of dough and place on a parchment-lined baking sheet, spacing about 3" apart (you can also form dough into ping pong–sized balls with your hands). Do not flatten; cookies will spread as they bake. Place prepared pan into refrigerator for 30 minutes.

Bake cookies until edges are golden brown and firm but centers are still soft, 11–12 minutes. Sprinkle with sea salt. Let cool on baking sheets 10 minutes, then transfer to a wire rack and let cool.