This is my favourite among the dishes made out of karunaikizhangu, the other one being karunaikizhangu masiyal, my sister Sabi's favourite! I have never personally made this dish as the slightly itchy karunaikizhangu is not relished in my inlaw's place but I love to hog it whenever Amma makes it for me.
Mustard seeds (கடுகு) - 1 tsp
Urad dall (உளுத்தம்பருப்பு) - 2 tsp
Dry red chillies (காய்ந்த மிளகாய்) - 4
Tamarind (புளி) - 2 inch strip / 2 tsp of pulp
Asafoetida (பெருங்காயம்) - 1/2 tsp
Turmeric powder (மஞ்சள் பொடி) -1/2 tsp
Salt (உப்பு) - to taste
Gingelly Oil (நல்லெண்ணெய்) - 2 tsp
Peel the yam and cut into small round pieces. Wash well and pressure cook in water adding turmeric powder. It should be well cooked with two whistles. Take out the cooked yam, drain the water completely and let it cool.
In a kadai take oil, add mustard seeds and when it crackles, add the urad dall, let it become golden, add the red chillies and switch off the gas. Put these in a mixie along with tamarind, salt and asafoetida and grind.
Mash the cooled yam with a masher and add the ground mixture to it. Mix the whole thing together and your karunaikizhangu thuvayal is ready to eat with hot rice and gingelly oil!