wash the yam and peel the skin, apply some oil on your hands or wear gloves to avoid itching .
Chop yam into small cubes and wash again.
In the pressure cooker add the chopped yam pieces ,, enough water to cover the yam pieces and a piece of tamarind or lemon slice and cook for 3 whistles on medium heat.
Open the cooker when cool down and check if its done or not. mash few yam pieces with the back of the ladle.
in a bowl add yogurt and wheat flour and whisk it well and then dilute it with a cup of water, keep aside.
Heat oil in the cooking pan and add cumin, carom seeds, asafoetida, cloves, dry red chilies , and then curry leaves and chopped green chilies. stir to mix.
Now lower the heat and add turmeric and red chili powder, and immediately pour the boiled yam mixture along with the water from the cooker.
Now add the prepared yourt mixture and mix , now keep stirring till it start boiling , if you leave at this stage then the curd may curdle.
Once the curry start boiling then add ginger, coriander powder and salt and mix. let it cook on medium heat for around 5-6 minutres.
Add lemon juice and chopped coriander and switch off the heat.
Enjoy with partha, poori , roti or rice.