Drain chickpeas and dates. Add to a food processor with peanut butter, oats, vanilla, baking powder, and salt.
Blend until smooth — scrape down sides as needed. The batter will be thick.
Fold through walnuts if using.
Spread into a lined 20cm square tin. Press flat with wet hands.
Bake at 180°C for 20-25 minutes until golden on top and a skewer comes out mostly clean. They'll firm up as they cool.
Cool completely in the tin before slicing — at least 30 minutes.