Wash and wipe the bhindis, then cut it into the long slices and keep aside.
Heat 2 tbsp oil in a pan. Add sliced bhindis, salt and stir fry it on medium flame for 5-6 mins or till becomes non-sticky and cooked. Remove it from the pan and keep aside.
In the same pan heat the remaining 2 tbsp oil, then add cumin seeds, mustard seeds, nigella seeds, fennel seeds, fenugreek seeds and sautee it for few seconds.
Now add pinch of hing, ginger paste, finely chopped onion and sautee it till golden brown and soft. Add chopped tomatoes in it and again sautee it till soft and mushy.
Add red chili powder, turmeric powder, coriander powder and mix it well, and stir fry it till oil start leaving from the mixture.
Add the whisked yogurt and mix it well, stir it continuously for 3-4 mins or till starts boiling.
Now add the shallow fried bhindis in it. Add salt as per taste, mix it and cook it for 2-3 mins on low flame.
Achari Dahi Bhindi is ready, garnish it with chopped coriander and serve as a side dish with roti, paratha or dal rice.