Heat 1 Tbsp oil in a pan, add bengal gram, split gram dal, cumin seeds and coriander seeds and stir fry for couple of minutes or till the dals turn red. Remove and keep aside.
In the same pan, add garlic, red chillies, green chillies, coriander leaves and curry leaves and fry on medium heat for a minute. Remove and keep aside.
In the same vessel, add the remaining oil, add the chopped bottle gourd cubes and sauté for until the rawness of the vegetable goes and the water evaporates. Remove and cool.
Once cool, grind the dals first till coarsely ground, add the rest of the sautéed ingredients including the bottle gourd along with tamarind extract, sugar and salt and grind to a paste.
Heat ½ tsp of oil in a pan, add mustard seeds and let them splutter, add black gram dal and let it turn red, add curry leaves and dry red chillies and stir fry for a few seconds.
Pour the seasoning over the ground chutney and serve with hot rice.