Start by preparing the banana stem. Cut off the outer layers until you reach the tender inner core. Then cut the banana stem into small round pieces. Remember to remove the fibres that come out while cutting.
Soak the chopped banana stem pieces in water to prevent oxidation.

Heat oil in a kadai or a heavy-bottomed pan over medium heat.
Once the oil is hot, add mustard seeds. Allow them to crackle. Now, add the green chillies and chopped onions. Sauté until the onions turn translucent.
Drain the soaked toor dal and add it to the kadai. Sauté for a couple of minutes.
Squeeze the water from the banana stem pieces and add them to the kadai.
Add salt and turmeric powder. Mix well.

Cover and cook for about 10 minutes on low to medium heat. Stir occasionally to prevent burning and ensure the banana stem cooks evenly.

Once the banana stem is cooked and tender, add the grated coconut. Stir well to combine.
Cook for another 2 minutes, then turn off the heat. Garnish with coriander leaves.

Your Vazhaithandu Poriyal or Banana Stem Poriyal is now ready to serve. Enjoy it as a side dish with rice or roti.

Notes

Adjust the green chillies according to your taste preference.
If the mixture is too dry while cooking, add a little water. Be careful not to add too much, as the banana stem will release some water.
The banana stem should be cooked until it’s tender but not too soft or mushy.