Line two half sheet pans with parchment paper; set aside.
For the brown butter, cut the butter into pieces and add to a 10-inch skillet (preferably light-colored so you can see easily when the butter has browned). Heat over medium heat, stirring as the butter melts so that it cooks evenly.
As the butter continues to cook, constantly and slowly stir with a silicone spatula. The butter will foam, sizzle, bubble, and after a few minutes (anywhere from 5 to 8 minute), the solids in the butter will begin to turn golden. Brown butter can burn easily, so don't walk away!
When the butter solids are browned and golden and it smells caramelly and fragrant, immediately remove the skillet from the heat and pour the butter into a large bowl.
For the cookies, to the bowl with the brown butter, add the brown sugar and granulated sugar. Stir to combine. Let the mixture sit until just barely warm or cooled to room temperature, 5 to 7 minutes.
Add the eggs, egg yolk, and vanilla, and stir until well-combined and the batter is light and creamy.
Add the flour, baking powder, baking soda and salt. Mix until a few dry streaks remain.
Stir in the chocolate chips until evenly combined. Let the batter rest while the oven preheats.
Preheat the oven to 350 degrees F. (Make sure the oven is preheated fully before baking the cookies - if the oven isn't hot enough, the cookies will likely spread while baking.)
Scoop the cookie dough into 2-tablespoon size portions (I use a #40 medium cookie scoop) and roll into balls. Place several inches apart on the prepared baking sheets.
Bake for 10 to 11 minutes until the cookies are just set around the edges and a bit crackly on top. For super soft and chewy cookies, don't over bake.
Immediately out of the oven, sprinkle a few grains of sea salt on each cookie, if desired.
Let the cookies cool for a few minutes on the baking sheets before removing to a wire rack to cool completely.
Notes
Flattening Cookies:if your cookies are flattening in the oven, increase the oven temperature by 25 degrees. I find these cookies bake best in my oven on standard bake vs convection bake, but you can play around with the oven settings on your oven to see what works best.Chilling Cookie Dough:these cookies can be baked right away. However, if you want to chill the cookie dough prior to baking, roll the cookie dough into balls prior to chilling, and add 1 to 2 minutes onto the baking time if baking the cookie dough straight from the refrigerator.