This is a classic Punjabi sabji. I have eaten aloo gobhi in many homes and restaurants, and like most homey dishes, I have never eaten two versions that taste the same. This is my recipe for making aloo gobhi.
Heat oil in a large frying pan or kadhai. Add onion, ginger, and garlic. Fry for a few minutes until golden brown. Finely chop the coriander stems and add to the kadhai. Add the green chillis.
Add the turmeric powder and fry for a minute. Now add the tomatoes. Cook a few minutes till the tomatoes are pulpy.
Add the potatoes. Fry for a few minutes till they are coated with the masala. Now add the cauliflower florets. Add the cumin and coriander powder, garam masala, red chilli powder, sugar, and salt. Add water , and stir well.
Bring the sabji to a boil, cover and reduce heat. Cook about 20 minutes till potatoes and cauliflower are very tender, but not mushy.
Check seasonings. If you feel the sabji is not tart enough, add the tomato puree.
Garnish with the chopped coriander leaves and serve.