Break the nuggets into small pieces. Peel and quarter the potatoes vertically. Grind the onions and ginger to a fine paste.
Heat the oil in a pressure cooker and add the cumin seeds. When they begin to change colour add the onion-ginger paste and sauté for three minutes.
Crush and add the nuggets and continue to sauté for five minutes, sprinkling a little water whenever the mixture turns a little dry.
Add the tomato puree and sauté till the oil surfaces. Add the turmeric powder, coriander powder, red chilli powder and salt and mix well. Add potatoes and sauté for two minutes.
Stir in two cups of water and let it come to a boil. Cover the cooker and cook till pressure is released two to three times (two to three whistles).
Open the lid when the pressure has reduced completely. Sprinkle the garam masala powder and fresh coriander and serve hot.