Chop the onions finely. Puree the tomatoes. Slit the green chilli. Boil the moong sprouts in very little water. Do not overcook. Drain and keep the moong water aside.
Heat butter in a tava and add the onion and sauté. Add the ginger garlic paste and fry till the onion turns golden. Now add chilli powder, turmeric powder, green chilli and sauté for few seconds. Now add the tomato puree, boiled potatoes, pav bhaji masala, garam masala powder and salt and cook for 5 minutes.
Add the moong sprouts and chopped coriander and cook for atleast 15 to 20 minutes over slow flame for all the flavors to meld together and form into a smooth mixture. If the mixture becomes dry, sprinkle the moong water.
Serve hot with bread or rotis with dollops of butter, onion rings, lemon wedge, coriander leaves sprinkled over them.