• The dough can be made by hand, with a stand mixer, or with an electric hand mixer.

Prep

• Line a cookie sheet with parchment paper.
• Preheat the oven to 400°F/205°C.
• Measure 475 g (5 cups) old-fashioned oats and add them to a food processor fitted with a blade attachment. Pulse until the oats are ground into a fine powder. Remove the oats and add 170 g (1 cup) chocolate chips to the food processor. Pulse a few times to give the chips a rough chop.

Mix

• Add 226 g (2 cups/4 sticks) unsalted butter, 400 g (2 cups) sugar, and 200 g ( 2 cups, packed) brown sugar to the bowl of a stand mixer fitted with the paddle attachment. Mix on low speed, gradually increasing the speed to medium until the butter and sugars are creamed together.
• Add 62 g (½ cup) sourdough starter discard, 4 large eggs, and 2 tsp vanilla extract to the bowl and mix on medium speed until completely incorporated, scraping the sides of the bowl as needed.
• In a separate bowl whisk 500 g (3 cups) flour, 2 tsp salt, 2 tsp baking soda, and 2 tsp baking powder together.
• Add the dry ingredients into the wet ingredients and mix until fully combined. Mix in all the ground oats and the remaining chocolate chips. Be sure all of the ingredients at the bottom of the bowl are mixed in well.

Scoop and Bake

• Use a cookie scoop to scoop cookie dough onto the parchment-lined baking sheet 2 inches apart. Place in the oven and bake for 11-13 minutes. The cookies are done when the edges of the cookies just begin to turn golden brown, while the center still looks soft and doughy.
• ​Remove the cookies from the oven and allow to rest on the baking sheet for 2 minutes before removing them to a wire rack to cool.