Take a non stick pan and add sesame seeds, tumbur and dry red chilies.
Dry roast on low heat until aromatic.
Take out off the pan, otherwise they may burn as the pan is very hot.
Once cool completely, grind to a powder. Keep aside this spice powder.
Take curd in a bowl and whisk it. If the curd is thick, you can add little water.
Add salt and spice powder.
Whisk well so that everything gets mixed.
Then add potatoes, onion, coriander leaves and green chilies.
Give them a good mix.
For tadka, add mustard oil in a tadka pan.
Let oil cook to the smoking point.
Add Fenugreek seeds.
Let the seeds burn to black. Yes, not brown but burn to black.
Take the tadka pan off the heat and come close to the curd pan.
Add turmeric powder and mix. Do fast as the oil is very hot, so turmeric will burn.
Immediately pour this tadka over the curd.
Mix well.
Enjoy with steamed rice.