Drain the chickpeas and sweetcorn, then tip into a food processor. Pick the coriander leaves, adding half the leaves and all the stalks to the processor.
Add the spices, flour and a pinch of sea salt, finely grate in the lemon zest, 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 4 equal-sized patties, roughly 2cm thick. Place in the fridge for 30 minutes to firm up.
Heat a splash of oil in a large frying pan over a medium heat, add the patties and cook for 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. Delicious served with a fresh green salad.