Preheat oven to 350 degrees, and line an 8 inch x 8 inch baking pan with parchment paper.
Pulse oats in food processor until they're the consistency of coarse flour (a few larger pieces are okay). Add remaining dry ingredients and pulse to combine. Transfer to a bowl.
Combine wet ingredients in food processor, and blend until smooth. Scrape down the sides of the bowl as needed.
Add the dry ingredients to food processor and pulse until everything is combined. The batter will be thick and sticky. Fold in walnuts and chocolate chips.
Spread the batter into the lined pan. Bake for 28-32 minutes, inserting a toothpick (or knife or chopstick) into the center to test for doneness.
Remove from oven and let the brownies cool in the pan for 15 minutes. Transfer to a cooling rack, and cool completely (if possible) before cutting into 16 squares.
Tips and SubstitutionsIf you have brewed coffee on hand, replace 2 tablespoons of the milk with coffee for enhanced chocolate flavor.For peanut-free brownies try these with sunflower seed butter instead of peanut butter.If you're interested in reducing the sugar or choosing unrefined options, check out Hu brand chocolates, and use coconut or date sugar instead of brown sugar.StorageStore leftover brownies in an airtight container in the refrigerator for up to 5 days. They can also be frozen for longer storage.*This recipe was originally published in September 2018 and has been updated with new photos and instructions.