Start by making the brown butter. Place both sticks of butter in a small saucepan or light-colored skillet. Heat over medium heat, stir gently as the butter begins to melt. And continue stirring occasionally after the butter has completely melted. Continue to cook until the butter has turned golden brown, the foam on top has slightly subsided, and the milk solids on the bottom of the pan have toasted. It will smell intensely buttery, nutty, and rich.
Just be sure to keep a close eye on your butter as it browns. Mine is usually done within 5 minutes, but it can cook faster or slower, so be sure to watch it closely—you don’t want to burn your butter!
Remove the pan from the heat and allow your brown butter to cool for 5–10 minutes.
In a large mixing bowl, combine the white sugar, brown sugar, and egg yolks, and mix or beat until well combined. Add the vanilla extract, sourdough discard, and cooled brown butter, and mix well.
Now you can either mix your dry ingredients in a separate bowl or simply add them to your large bowl (which is what I usually do). Add the baking soda, baking powder, and salt, and mix well. Then add the flour and mix until combined.
Finally, stir in your chocolate chunks, mixing just until incorporated.
Place your cookie dough in the fridge to chill for 30 minutes.
Preheat the oven to 350°F.
Remove the cookie dough from the fridge and begin rolling it into balls. I usually use 1 tablespoon of cookie dough, but you could also use 2 tablespoons, depending on how big you want your cookies (you can also use a cookie scoop).
Place your cookie dough balls on a parchment-lined baking sheet, keeping a decent amount of space between each cookie (I usually bake 5–6 per tray).
Bake for 8–10 minutes, or until the edges are golden brown and the centers seem set.
Allow the cookies to cool for 3–5 minutes on the baking sheet before transferring them to a wire rack. Repeat with the remaining cookie dough.
Serve warm with a glass of milk, or allow the cookies to cool to room temperature.
Enjoy!