In a bowl, add cumin, coriander, turmeric, garam masala, chilli powder, methi, sea salt and water. Mix briefly.
Heat 1 tablespoon of oil in a large frying pan or wok. Add the prepared spices and the chopped onion. Stir-fry for 2-3 minutes.
Add the garlic & ginger paste and green chilli. Stir-fry for 2 minutes.
Add the crushed tomatoes. Stir-fry for 1-2 minutes. Add the chickpeas and 150ml water and mix well. Add the parboiled potatoes, mix well and simmer for 10-15 minutes.
Add the lemon juice and fresh coriander. Serve the curry with fresh chapatis and chilli pickle on the side.