Baby Little Gem leaves make a perfect vessel for a canapé – especially the inner ones, when they aren’t too floppy. You should get around 6–10 good leaves per lettuce. If you can’t get a green mango use half regular mango and half cucumber or jícama, or try green papaya. The black beans are Chinese, and the ones you want to look for are salted whole beans, rather than black bean sauce – although the latter will do at a pinch.