Soak the chana/ chole overnight and cook till soft but firm. Take a handful of the chana and mash well. Keep aside.
Heat a non-stick pan or kadai. Add the ustard seeds. When they splutter/ pop, add the cumin, coriander and turmeric powders and lightly roast for less than a minute. Take care they do not burn.
Quickly add the grated onion, chopped tomato, ginger julienne, garlic paste and chilli powder along with a quarter cup of water. Mix well an allow to cook for about 5 minutes till the water evaporates, while stirring occasionally. By now the raw smell of the onion should have disappeared. If not add about 2 tbsps of water and cook till the water has almost evaporated, again stirring frequently.
Now and add the cooked chana, salt and a cup of water and allow to simmer for about 5 minutes till some of the water evaporates. Add the mashed chana and the garam masala and simmer for a few minutes till the Kabuli Chana has a thick gravy.
Garnish with chopped coriander and serve hot with pooris, chappathis or rice.