Note: If doubling or tripling this recipe the amounts in the instructions will not be accurate. You will have to double or triple the steps yourselves. Ex: Step one says melt 10 tablespoons of butter. If you are doubling you will need to do 20 tablespoons and if tripling 30 tablespoons.
Preheat oven to 375°F. Line two cookie sheets with parchment paper.
In a large skillet or sauce pan, melt 10 tablespoon of butter over medium heat. Continue to cook over medium heat until the butter is a dark brown color and smells nutty (it will sizzle and foam as it cooks). Remove from heat and add the remaining 4 tablespoon of cold butter. It will foam a lot, so whisk constantly until the foam subsides.
Using a stand mixer or hand mixer on medium speed, mix the warm butter with both sugars, salt, and vanilla for 30 seconds. Add the egg and egg yolk and mix on medium speed for 1 minute. The mixture should be thick, smooth, and glossy.
Whisk flour and baking soda in a small bowl to remove lumps. Add to wet ingredients and stir by hand with a rubber spatula until mostly combined.
Add chocolate chips and nuts, if using. Continue to stir by hand until just combined. Do not over mix.
Using a 1½ tablespoon scoop, scoop cookies onto the prepared cookie sheets. Bake for 8-10 minutes, or until the center is puffy and the edges are just starting to brown. Don't over bake.
Leave cookies on the cookie sheet for 3-5 minutes, then transfer to a cooling rack.