Melt butter in a medium sauce pan over medium-high heat. Continue to heat as butter starts to bubble - the bubbling sounds will get louder as the butter heats up. Stir constantly, scraping the bottom and sides of the pan with a spatula as you go. Keep a close eye on it as it will change color quickly. Once the butter turns a nice dark golden brown and has a nutty aroma, remove it from the heat. Transfer butter to a heat-proof bowl and let cool. You may place it in the fridge for 15-20 minutes to speed up the process.

Preheat the oven to 375 degrees F.

Combine flour and baking soda in a medium bowl and set aside.

Once butter is cooled, but not hardened, place in the bowl of a stand mixer, along with both sugars, salt, and vanilla. Mix until light and fluffy, about 3-5 minutes.

Add egg and egg yolk and mix until combined.

Mix in flour mixture until just combined.

Stir in chocolate chips with a spoon or spatula.

Scoop 2 Tbs of dough at a time onto a baking sheet lined with parchment paper. You'll need to do at least two separate batches in the oven. Should make about 24 cookies.

Bake for 9-12 minutes, till the edges just start to brown. [UPDATE: Definitely aim to bake these on the lower end of that timeframe, depending on how big your cookies are and how your particular oven bakes. I usually bake mine 8 minutes, check on them and rotate the pan and only bake them one additional minute. These cookies are divine when removed from the oven when the edges are starting to brown. Letting them cool on the pan for a bit while salting them will ensure they're baked through.] Remove from oven, sprinkle with additional salt, and let cool a few minutes before removing from the pan.