Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, cream together butter, brown sugar, and granulated sugar until light and fluffy.
Mix in sourdough discard, egg, and vanilla extract until fully combined.
In a separate bowl, whisk together flour, baking soda, and salt.
Gradually add dry ingredients to wet ingredients and mix until just combined.
Fold in chocolate chips evenly throughout the dough.
Scoop dough onto prepared baking sheet, spacing evenly apart.
Bake for 10–12 minutes or until edges are golden but centers remain soft.
Cool on the baking sheet for 5 minutes before transferring to a wire rack.