Soak chickpeas overnight in water .Pressure cook the chickpeas until tender.Grind together the tomato and onion. Heat oil in a pan.Add the chopped ginger,garlic,onions,saute till translucent.Now add the onion-tomato paste,red chiily powder,coriander powder, the cooked chickpeas and salt. Mix well so that the chickpeas are nicely coated in the gravy. Add the garam masala and mix again.Remove from heat and garnish with coriander leaves