In a medium saucepan, melt the butter over medium-low heat until completely melted. Increase heat to medium and continue to cook the butter, stirring or swirling frequently until brown bits begin to appear at the bottom of the pan. The butter will foam on top so you will need to use a spoon to check the butter frequently while it is browning. Remove the browned butter from the heat and transfer to a heat-proof bowl to cool to room temperature.
1 cup salted butter
In a large bowl, whisk together the cooled brown butter, granulated sugar, and brown sugar until well combined.
¾ cup (150g) granulated sugar, 1 cup (200g) light brown sugar
Add the sourdough discard, eggs yolks, and vanilla extract, whisking well.
2 large egg yolks, ¾ cup sourdough discard, 2 teaspoons pure vanilla extract
Stir in the flour, baking powder, baking soda, and salt.
2¾ cups (388g) all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, ½ teaspoon salt
Stir in the chocolate chips until evenly dispersed throughout the cookie dough. Use a medium cookie-scoop to scoop balls of dough onto a baking sheet lined with parchment paper.
2 cups semisweet chocolate chips, Flaky sea salt
Chill the dough balls for at least 1 hour (or up to 72 hours) or freeze for 20 minutes (or up to 3 months).
Preheat the oven to 375°F. Line two baking sheets with parchment paper.
Transfer the balls of dough to baking sheets lined with parchment paper, spacing them a few inches apart so they have room to spread. Bake for 10-12 minutes until golden brown around the edges. Do not overbake. Sprinkle the warm cookies with flaky salt.