Heat the oil in a non-stick pan and add half the onions and sauté till lightly browned. Add the garlic and stir-fry for a minute. Add the mutton mince, ginger, green chilli, coriander powder, cumin powder and red chilli powder.
Sauté for five minutes, breaking up any lumps if formed. Add three-fourth cup of water, bring to a boil. Cover, lower the heat and simmer for half an hour. Add the peas, salt, garam masala powder and another one cup of water.
Mix well and simmer, covered, for about ten minutes till the peas are cooked well. Take a roti, apply butter and green chutney evenly. Spread the kheema filling.
Drizzle some tomato ketchup and lemon juice. Sprinkle fresh coriander, remaining onions and chaat masala. Roll tightly so that the filling remains secure in the roti. Wrap in an aluminium foil and serve.