In a wide cooking vessel add the veggie cubes and some water. Add tamarind water and curry leaves to it.
Next add jaggery, turmeric powder and salt. Let it cook in medium flame till the jackfruit pieces turn soft.
Meanwhile, heat a pan adding blackgram lentils (urad dal). Roast it till it turns little brown. Take it in mixer.
Add coriander seeds, cumin seeds, red chillies and coconut to the same mixer.
Adding enough water, grind them together to fine puree. This is the coconut masala for the curry. Add this to cooked veggie.
Combine everything well. Adjust salt. Adjust consistency by adding required water. Bring it to nice boil.
Finally heat a tempering pan adding all the ingredients under "To temper" list. When the mustard seeds splutter, pour it to jackfruit curry. Very delicious jackfruit curry is ready to serve to steamed rice.