Got this straight from here - http://www.route79.com/food/channa-masala.htm (has step-by-step pictures). So yummy :)
2 tins of ready-boiled chickpeas - rinsed in a colander
1 tin of chopped tomatoes
1 large onion chopped into long thin strips
3 medium potatoes, peeled and chopped into bite-sized chunks
Chunks of frozen, pre-pulped garlic, ginger and green-chillie
Spices: Turmeric (halidi), Garam Masala, Ground Coriander, Salt
Seeds: Onion seed and Cumin (Jeera) seeds.
A large large pot in which to pour 2 or 3 tablespoons of vegetable oil
Heat the oil in the pot until hot. Add the onion and cumin seeds and watch them pop and fizzle for around 20 seconds. Then add the chopped onions and fry until they are lightly browned. Then add the frozen (and by now thawed) chunks of pulped ginger, garlic and chillie. Stir fry on medium heat.
Then add the tin of chopped tomato and stir-fry for about 5 mins on medium-to-high heat until the oil starts to separate from the onion/tomato mixture - and then add the spices:
2 teaspoons of salt
2 teaspoons of ground coriander
2 teaspoons of garam masala
1.5 teaspoons of haldi (turmeric)
Stir it all thoroughly on medium flame.
Then add the chunks of potato - stir until well coated in spices. Then add around 3 smallish glasses of water into the pot - and put the lid on and bring to boil. Let it simmer on a very low flame for around 20 mins with the lid on. This will soften the potato.
After about 20 mins - check to see that the potato chunks are soft - and then add the drained (already-boiled) chickpeas. Stir it all up - and add another small glass of water to the pot. Bring to a fierce boil and then turn the flame down to simmer the pot for a while - with the lid partially on.
After about a further 15 mins of simmering - add some freshly chopped (or frozen) fresh coriander leaf and stir it all in. Keep it simmering for about 10 mins more. After that - turn off the heat - put the lid on tight - and let it it stand for around 15 mins whilst you make some basmati rice - or warm some pitta bread etc. It's then ready to serve!