Heat up your pan and add the oil. When it starts to shimmer, add the onion and green chilli. Season with salt and cook on a medium flame until only just starts to turn golden (should take about 3-4 mins)
Add the ginger and garlic and fry until it doesn't smell raw anymore. Add all the dry spices (turmeric, chilli, coriander and cumin) and fry for a minute on low flame, careful not to burn them.
Add the tomatoes and mix through nicely. Cook until all water has evaporated and you can start to see oil separate from the sides of the cooked tomatoes.
Add the cooked chickpeas with about 2-3 tablespoons of the cooking liquid or hot water. Adjust the salt and sugar for balance. Let it simmer gently for 3-4 minutes covered