Preheat oven to 350°F. Line a 9x13 pan with parchment or grease pan.
Using a mixer, cream together butter and sugars. Add sourdough starter, eggs, and vanilla, mix well.
In a small bowl, whisk together flours, baking soda, and salt. Add flour mixture and combine well. Add oats, mixing on low until just combined. Add 2 cups chocolate chips and mix until just combined.
Spread mixture in pan and sprinkle with remaining chocolate chips. Bake for 20-35 minutes, until just baked. Allow to cool, slice, and serve! Bake about 25 minutes for chewy texture.
