Place the chickpeas into a large container and cover completely with cool water; let stand 8 hours to overnight.
Drain water from chickpeas and transfer them to a pot; cover with water. Bring water to the boil; reduce heat and simmer until chickpeas are tender, about 1 hour. Cool chickpeas until easily handled.
Combine chickpeas, fresh coriander, eggs, garlic, chickpea flour, tahini, ground coriander, salt, cumin and chilli powder in a blender; blend until well mixed but still chunky. Form mixture into burgers.
Heat oil in a large pan over medium heat; fry burgers until golden and crisp, about 3 minutes per side.