Using a saucepan over medium heat add the unsalted butter. Allow the butter to melt with occasional stirring of the pan. Cook the butter for 5-8 minutes. The butter will begin to brown when foam occurs. Once you notice a nutty scent, remove the butter from the heat. Add the brown butter to the bowl of an electric mixer.
In a separate bowl, whisk together the all-purpose flour, baking soda, and kosher salt. Set aside. Line a large cookie sheet with parchment paper.
Using an electric mixer on medium speed, mix together the brown butter, granulated sugar, and brown sugar. Mix until well combined. Beat in the eggs and vanilla extract. Beat until fluffy.
Mix in dry ingredients into well combined. Fold in the chopped chocolate.
Using a large cookie scoop, scoop the dough onto the prepared cookie sheet. Wrap the cookie sheet in plastic wrap, let the dough rest in the refrigerator for at least 2-48 hours. (This process allows the flavor to develop.)
Preheat the oven to 375 degrees F. Line another cookie sheet with parchment paper.
Arrange the cookies onto the cookie sheet leaving 2 inches of space between each cookie and away from the edges of the baking sheet.
Bake the cookies until golden brown with crispy edges, roughly 8-11 minutes. Allow the cookies to cool for a few minutes before transferring to a wire cooling rack. (If desired, sprinkle flaky salt onto the cookies immediately after baking).