For preparing Chembu Thandu Pachadi, first clean, Wash and cut the Tomatoes into small pieces and keep them aside.
Grind the Coconut along with Green Chilli, Mustard seed and some Water and keep this paste separately.
Remove the outer portion of Chembu slightly and cut them into small pieces. Pour some Salt on top of these pieces as shown in above pictures and keep it aside for about 5 – 10 minutes.
After about ten minutes, mix the Chembin Thandu pieces and Salt well (for avoiding the irritation of Chembin Thandu, use gloves or some other method). Extract the water left in the Chembin Thandu pieces and then keep these pieces separately.
Change the Chembin Thandu pieces into a cooking vessel. Add Tomato pieces, Turmeric powder and Salt along with two cups (or as required) of water. Cover the cooking vessel with a plate/lid of the cooking vessel and cook the mix for about 10 – 15 minutes in medium flame.
After about 15 minutes, take the cooking vessel out from the stove and if the Chembin Thandu pieces and tomatoes are cooked properly, add the ground coconut and stir it well. Similarly add Curd also and stir it (Pachhadi) further.
Heat Oil in a Frying pan/Cheenachatti and burst the Mustard seeds in this hot oil, fry the Red Chilli pieces also in this Oil and add this Mustard seeds and Red Chilli pieces into the Pachhadi along with the Oil left in the Frying pan/Cheenachatti.
Chembin Thandu (Colocasia Stem) Pachhadi is ready. Garnish this Pachadi with Curry leaves and serve it along with Chappathi/Poori/Cooked Rice etc.