There will be an outer ring in banana stem.Remove the outer ring ,so that there are no more rings seen in cross section.
Slice thinly into disks,meanwhile removing the fibre with help of fore finger, by rolling around it, for each disk.
Keep the cut slices immersed in water mixed with the beaten curd (buttermilk), to prevent change in colour.You can replace buttermilk with a squirt of lime/lemon juice.
Chop the slices finely and mix it in a plate, with moong dal,salt and turmeric (if adding) and mix well and keep aside for 10 mins.
In between mix one more time giving pressure to the mixture and keep the plate slanting, because the mixture will leave out lots of water from it.
After some time, squeeze out gently and keep it aside the excess water. No need to squeeze out completely as some nutrients will be lost.
Heat the kadai and add the tempering items followed by curry leaves.
Add banana stem, strained from water. Gently squeeze and add.
Fry for one or two minutes and tightly press in the kadai and cook covered till soft. You can sprinkle the reserved water for cooking the stem if needed.
You can notice that it has become transparent after it gets cooked. To check the doneness, press between your fingers and test. Or pop one piece inside your mouth and taste.
Lastly add the grated coconut.Mix well and put off the flame and transfer to the serving bowl!