Peel off the outer layer of fiber from the banana-tree-stem and chop it into fine pieces.
Wash and keep aside.
Heat oil in a kadai or a pan
Add mustard seeds and when they start to splutter, add curry leaves and stir.
Add the chopped stem pieces, turmeric, salt and chilly powder.
Cover it with a lid and allow it to cook.
Grind together the grated coconut and garlic in a chopper or mixie (dry without water).
When the stem pieces are almost cooked, add the coconut-garlic mixture to it and cook again with lid closed, till completely cooked.
When done, put off the flame and sprinkle coconut oil over the dish and mix.
Keep aside for a while with lid closed, before serving.