Remove the skin of the banana stem, which will look like a separate ring as shown in the pic.
Then cut into thin circles / slices. If you want you can remove the fiber part as you cut. Otherwise, you can refer Top tip section above.
Chop vazhaithandu finely. Keep immersed in lemon squeezed water in a bowl until use.
Grind coconut, green chilli, jeera and rice flour with little water to a smooth paste.
Boil water and cook the banana stem with salt.
Once done, add the ground coconut paste and mix well. Bring to boil and switch off the flame.
Add the curd (beat well smoothly) and mix well.
Temper with the items given under to temper table. Pour over the kootu and mix in.