Recipe and image courtesy of Chef Virginia Willis
Heat the oven to 300°F. Lightly grease one round 9" cake pans with Baker’s spray. Set aside. In a medium-sized bowl, beat together the peanut butter, oil, sugar, and vanilla; beat in the flour. The mixture may seem a little dry at first; keep beating till it comes together. If it absolutely won't come together, dribble in up to 1 tablespoon of water, until it does. (This is a crumbly and stiff dough.) Place in pan and press out dough.
Use a fork to prick the dough all over; this allows any steam to escape, and prevents the shortbread from bubbling as it bakes. Bake the shortbread until it's a light golden brown across the top surface, and a deeper golden brown around the edges, about 35 minutes.
Remove it from the oven, and immediately turn it out onto a clean work surface. Using a pizza wheel or sharp knife, cut each round into 6 wedges. (Do this while the shortbread is still warm; if you wait until it's cool, it won't cut easily.) Transfer the shortbread wedges to a rack to cool.
Serve as is, or decorate. You can drizzle with melted caramel or melted chocolate and sprinkle with additional nuts!