In the same large bowl with the cooled brown butter, add the sugars and use a silicone spatula to mix together. Add the egg, egg yolk, and vanilla and mix well.
Add in the flour, baking soda, and salt and fold until no streaks of flour remain, being careful not to overmix your batter (it will mix some more when you add the chocolate).
Fold in the chocolate until evenly distributed. Do not over mix! Cover and transfer to the fridge for at least 30 minutes or overnight.
Preheat the oven to 350°F. Line a baking sheet with parchment paper.
Remove dough from the fridge and let it sit out until it’s scoop-able, about 20 minutes. Scoop into 14 (2 oz) balls, roll them in your hands, then place on the baking sheet 2-inches apart. I prefer to bake 6 at a time.
Bake until the cookies have puffed up and are very light golden brown around the edges but still somewhat soft in the middle, 10-14 minutes.
Remove the baking sheet from the oven, sprinkle with flaky sea salt (if using), and allow the cookies to cool slightly before serving.
They’re best just warm with a glass of cold milk or topped with a scoop of vanilla bean ice cream.