Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar using an electric mixer or whisk until light and fluffy.
Add the sourdough starter, egg, and vanilla extract to the mixture and mix well until combined.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, and stir until just combined.
Fold in the chocolate chips until evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, leaving enough room between each cookie to spread.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown.
Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes before transferring them to a cooling rack.