Cut the padwal in small size along with it's skin, then put the all veggies (onion, ginger, garlic and green chillies)in a mixer, and mix it. You can add little bit of water if needed.

Heat the oil, put kala jeera, saute it. Then add a little amount of chopped garlic. After a few minutes, saute and add the paste and stir it on medium flame. Then add salt, little bit sugar to balance, you can avoid the sugar if you want. Then stir it again. Now leave it on low flame. It will take time but slow cooking is important for this dish. When oil comes out and the paste becomes medium dry and it's colour changes then it will ready.