In a large bowl, combine softened butter and sugars. (Butter should be soft enough to mix by hand)
Add the egg and stire until incorporated
Stir in the sourdough starter and vanilla extract
Add flour, salt, and baking soda. Mix carefully and avoid overmixing
Fold in the chocolate chips. Refrigerate dough for at least 15 minutes, or up to overnight for a more cake-like texture
When ready to bake, preheat over to 350 F (let refrigerated dough come to room temperature before baking)
Drop spoonfuls (2-3 tablespoons) of dough onto a parchment-lined baking sheet. A 3 tablespoon ice cream scoop works well