Chewy, gooey cookies with a hint of tang that makes the chocolate and brown butter flavors pop. Your new favorite cookie recipe.

Brown the butter: melt butter in a saucepan over medium heat, stirring frequently. Continue cooking until it turns golden and smells nutty. Pour into a bowl and let cool for 10 minutes.
Whisk the brown butter with both sugars until smooth.
Add the sourdough discard, egg, egg yolk, and vanilla. Whisk vigorously for about 1 minute.
Add the flour, baking soda, and salt. Stir until just combined. Fold in the chocolate chips.
Cover the bowl and refrigerate for at least 1 hour (or up to 72 hours — the flavor gets better each day).
Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.
Scoop rounded tablespoons of dough onto the prepared sheets, spacing 2 inches apart.
Bake for 11-13 minutes until the edges are set but the centers still look slightly underdone.
Immediately sprinkle with flaky sea salt. Let cool on the baking sheet for 5 minutes before transferring to a wire rack.