Dry-roast the urad dal for grinding if it is not already roasted. Scrub the ridge gourds thoroughly, then peel them. Reserve the peels for the chutney.
Heat 1 tsp oil and stir-fry the peels for 2–3 minutes. Add salt and fry for another minute. Set aside to cool for a bit.
Grind the stir-fried peels with the grated coconut, green chillies, tamarind and roasted urad dal to a smooth chutney, adding a little water as needed. Add the optional garlic if using.
Serve as it is, or prepare the optional tadka. Heat a little oil, add the mustard seeds and urad dal, and let the mustard seeds splutter and dal turn golden. Add the curry leaves and dried Byadagi chilli, then pour over the chutney.
Serve with lunch or dinner. I like it alongside peere kodhel and happala papad.