Preheat your oven to 375°F (190°C). Line two large baking sheets with parchment paper or silicone baking mats. Set aside.

In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), cream together the softened butter, light brown sugar, and granulated sugar on medium speed until light and fluffy, about 2-3 minutes.

Beat in the large egg and vanilla extract until well combined. Scrape down the sides of the bowl as needed.

Add the unfed sourdough discard to the wet ingredients and mix on low speed until just combined. Do not overmix.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined and no streaks of flour remain. Be careful not to overmix the dough.

Fold in the chocolate chips with a rubber spatula until evenly distributed throughout the dough.

Using a 1.5-tablespoon cookie scoop or two spoons, drop rounded balls of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.

Bake for 10-12 minutes, or until the edges are lightly golden brown and the centers are still slightly soft. They will continue to set as they cool.

Remove the baking sheets from the oven and let the cookies cool on the sheets for 5 minutes before transferring them to a wire rack to cool completely.