Heat the oil in a saucepan.
Add the mustard seeds, and when they sputter, add the onions.
Stir-fry until the onions are translucent.
Now add the green chillies, ginger and garlic. Stir-fry for another minute.
Add the greens and turmeric and saute until wilted, a couple of minutes.
Add the cooked dal and salt to taste. Add a cup of water to the pot and more to get the dal to your desired consistency.
Bring to a boil, lower the heat, and continue to simmer about 5 minutes.
Garnish, if desired, with coriander. Serve hot with rice or chapatis.