1. Preheat oven to 350 degrees F. Line an 8x8 baking pan with parchment paper.
2. Puree white beans and oil in a food processor fluffy, scraping the sides as needed.
3. Combine bean mixture, eggs, yolk, sugar, baking powder, and vanilla. Whisk until well combined. Stir in ground walnuts.
4. Pour mixture into prepared pan. Sprinkle chopped walnuts and chocolate chips on top of the batter.
5. Bake for 35-40 minutes. Let cool in the pan.