Soak the cut plantains in warm water mixed with half teaspoon turmeric for ten minutes. Drain and cook the plantains with the remaining turmeric and salt. Grind the coconut well with cumin and add to the cooked plantains. Let it simmer. Meanwhile, heat the oil and pop the mustard seeds. Add the urad dal and the coconut reserved for garnish and stir till browned. Add this mixture to the eriserry and mix in the curry leaves.