Wash potatoes thoroughly and boil for eight to ten minutes. Peel and cut into cubes. Separate cauliflower into florets and wash them thoroughly.
Boil them in two cups of water for two minutes. Drain and keep it aside. Peel, wash and chop onions. Peel, wash and finely chop ginger. Wash and coarsely chop tomatoes.
Heat oil in a pan, add cumin and mustard seeds. When they start crackling, add onions and fry until golden brown. Add turmeric powder, salt, chopped ginger, coriander powder and red chilli powder.
Then add the chopped tomatoes. Cook till the tomatoes are soft. Add the potatoes and the cauliflower. Cook for a while and stir in the tomato puree mixed with two tablespoons of water.
Cover and cook for further ten minutes or until the vegetables are soft.