Pre-heat oil in a heavy bottomed vessel. Add mustard seeds and let them splutter. Add the methi and cumin seeds and let them turn brown.
Add the crushed garlic flakes and fry for a few seconds. Add the chopped onions and sauté till pink. Add salt, turmeric pwd and chilli pwd and combine.
Add the chopped tomatoes and cook for 5-6 mts. Now add the mango pieces and mix well till they are well coated with the masala mixture. Cook covered for 4-5 mts on medium heat.
Add water and cook on high flame for 5 mts. Reduce heat and cook further for another 8-10 mts or till the water evaporates.
Add the grated jaggery and cook for 10 mts on low flame till water evaporates and you get the curry consistency.
Serve with hot steamed white rice or rotis.