- Cook yam and bananas in butter milk with turmeric powder till they get soft. Add salt, grated paste of coconut to it and cook for few minutes. Heat the coconut oil. Add mustard seeds and curry leaves to it and stir for a few minutes. Add the buttermilk mixture to this along with the black pepper and fenugreek seeds. Mix well. The dish is ready to serve. Garnish with mustard seeds and curry leaves