Step 1 Place beans in a large bowl and mash roughly, leaving some texture. Add egg, breadcrumbs, parsley and cumin; mix until well combined. Wet hands to shape mixture into 4 patties.
Step 2 Spray patties all over with olive oil. Set a large non-stick frying pan over medium heat. Cook patties for 2–3 minutes per side, or until burgers are golden.
Step 3 Meanwhile, set a large grill pan over high heat. Spray eggplant, capsicum and zucchini with a light coating of olive oil. Grill veg for 2 minutes per side, or until lightly charred and tender.
Step 4 Spread each bread-roll half with hommous, then top with eggplant, capsicum, zucchini, a bean burger and rocket.
Step 5 Drizzle burgers with hot chilli sauce (if using) and serve.