• Preheat oven to 350°. Place parchment paper on a cookie sheet.
• In the bowl of a stand mixer with paddle attachment, combine sugar, brown sugar, butter, peanut butter. Cream together for a few minutes until light and fluffy.
• Add egg and mix until well incorporated.
• Add vanilla and sourdough starter and mix until just combined.
• In a large mixing bowl, mix dry ingredients together.
• Add the dry ingredients to the wet ingredients about 1/3 at a time, and mix until just incorporated.
• Roll the dough into balls and place on a prepared baking sheet.
• Using a fork, gently press the dough ball with the prongs of the fork. Then, turn the fork 90 degrees and press again to flatten and make a criss cross pattern.
• Bake for 12-15 minutes or until the edges begin to turn golden brown.
• Move to a cooling rack to cool.

Long Fermented Version

• The night before, mix together butter, sugar, peanut butter, sourdough starter and flour in a stand mixer bowl and cover. Allow the grains to ferment for 8-24 hours.
• The next day, preheat oven to 350.
• Add egg and vanilla to the sourdough starter mixture, and mix together well.
• Sprinkle the remaining dry ingredients into the bowl and stir.
• For best results, refrigerate dough for at least one hour or up to 24 hours prior to baking.
• Bake cookies for 10 minutes or until the edges start to turn golden amber color.