Drain and place the chickpeas and sweetcorn into a food processor. Pick the coriander leaves, then add half to the processor along with all of the stalks. Add the spices, lemon zest, flour and a pinch of salt, then pulse until combined, but not smooth – you want to retain a bit of texture.
On a flour-dusted surface, divide and shape the mixture into four equally sized patties (roughly 2cm thick). Pop onto a tray and place in the fridge for around 30 minutes to firm up.
Heat a splash of oil in a large frying pan over a medium heat. Once hot, add the patties and cook for around 10 minutes, or until golden and cooked through, turning halfway.
Meanwhile, click off, wash and spin-dry four nice lettuce leaves, then finely slice the tomatoes horizontally.
Squeeze a large dollop of ketchup onto the base of each bun (toast them if you like), then top with the burgers. Layer over a couple of slices of tomato, a lettuce leaf, a few coriander leaves and finally the burger tops. Serve with a crisp, green salad, if you like.