In a mixing bowl, mash the boiled chickpeas with a fork or potato masher.
Add the oats, chopped onion, green chillies, coriander leaves, vegan mayo, cumin powder, and salt. Mix well to combine.
Shape the mixture into patties.
Heat oil in a pan over medium heat.
Fry the patties until golden brown on both sides, about 4–5 minutes per side.
Assemble the burgers by placing the patty in the bun and adding lettuce and tomato slices.
Serve hot with your choice of sauce.