1. Brown the butter: Melt the butter in a saucepan over medium heat, swirling occasionally until it turns golden brown and fragrant. Pour it into a bowl and let it cool until it firms up but is still soft at room temperature.
2. Cream the butter and sugars: Using a mixer or whisk, beat the cooled brown butter together with the dark brown sugar and white sugar until the mixture is light and fluffy.
3. Add the wet ingredients: Mix in the egg, vanilla extract, and sourdough discard until fully combined and smooth.
4. Combine dry ingredients: In a separate bowl, whisk together the flour, baking soda, and salt.
5. Mix dry into wet: Gradually add the dry ingredients into the wet mixture, stirring just until no streaks of flour remain. Be careful not to overmix.
6. Fold in chocolate: Gently fold in the chopped chocolate chunks and chips.
7. Portion the dough: Scoop about 3 tablespoons of dough per cookie onto a parchment-lined baking sheet.
8. Chill for best flavor: Chill the dough for at least 1 hour and up to 24 hours. You can bake right away, but chilling deepens the flavor and helps the cookies develop their signature look and texture.
9. Bake: Preheat your oven to 350°F (175°C) and bake the cookies for 12–14 minutes, until edges are golden but centers still look soft.^‍‍
10. Finish and cool: Remove from the oven and, while still warm, sprinkle flaky salt on top if desired. Let the cookies cool on the baking sheet for 8–10 minutes so they set perfectly before transferring to a wire rack.

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