Place 1 teaspoon ground black pepper in a deep bowl. Pour in ¼ cup water. Mix well. When the water clears, drain. Set aside.
Fry fenugreek seeds without adding oil, and grind to a fine powder. Set aside.
Whisk 2 cups yogurt. Set aside.
Grind grated coconut, cumin seeds, and 2 green chilies to a smooth paste. Add a little bit of water, only if needed. Set aside.
Place raw bananas (and yam if using), curry leaves, 3-4 green chilies, ground black pepper, ground turmeric, and salt in a deep pan. Pour in water just enough to cover the veggies. Place the pan over medium flame and cook until water dries up.
Add in ground coconut, and mix well. Add more water to make a thick sauce. Cook again. Check the seasoning, and add more salt if needed.
When done, sprinkle with ground fenugreek, and remove from flame. Leave it to cool.
Once cooled, stir in the whisked yogurt.
Now to temper the spices, heat oil in a pan, and splutter mustard seeds. Add in dried red chilies and curry leaves. Fry for a few seconds.
Add the tempered spices to kalan and mix well. Serve with rice.