Wash the Arbi and boil them in a pressure cooker till you get 1 whistle.
Once the pressure has settled down, take out the Arbi and let it cool down.
Peel the skin of the Arbi. To do that remove the skin from the thick end and then slide the Arbi out of it's skin by pressing gently from the other end.
Cut the Arbi lengthwise into 2 halves.
Heat oil in a pan on medium heat. Add the sliced Arbi and fry them till light golden brown. Drain the excess oil on an absorbent paper.
Heat oil in a pan and add the Mustard seeds. When they start to splutter add Cumin Seeds, Carom Seeds (Ajwain), Fennel Seeds (Saunf), Fenugreek Seeds (Dana Methi), Nigella Seeds (Kalaunji) and a pinch of Heeng.
Fry them for a few seconds till they start to crackle.
Now add the finely chopped Green Chillies, grated Ginger and pureed tomatoes to the pan.
Cook till the raw aroma of the tomatoes goes away.
Then add Red Chili Powder, Turmeric Powder, Coriander (Dhaniya) Powder, Garam Masala, Dry Mango Powder (Amchur) and Salt to taste.
Fry the gravy for a couple of minutes till it is properly roasted.
Add 1 cup beaten curd along with 1/2 cup water and cook on low heat for 4-5 minutes.
Stir continuously while cooking, otherwise the the curd will curdle.
Finally add the fried Arbi slices. Close the flame and let it sit for 15-20 minutes. Add coriander to garnish and serve hot with roti, poori or paratha.