Chop Green Mangoes lengthwise. I have kept them with skin on - meaning I haven't peeled them because that way when you cook the mangoes they get soft and mushy. But, in case you want them without skin, you can peel off the skin. Keep aside.
In a small mixing bowl combine spices with a bit of water. Mix well to make a smooth paste.
Heat Mustard Oil in a skillet over medium-low heat. Add dried red chilies, cumin seeds, fennel seeds, fenugreek seeds, and nigella seeds. Let it sizzle for a while.
Now add the masala mixture and stir well. Cook until the raw spices are fully cooked.
Now add the chopped raw green mangoes into the skillet.
Toss well and allow the mangoes to cook. Add some water - as per requirement- and Cook well until the mangoes are firm but thoroughly cooked. Keep a close eye because they can become mushy in a matter of minutes.
Now stir in jaggery powder and mix well until it dissolves in the curry.
Once the mangoes are cooked but not mushy and soft, you can take it off the heat. Serve it on a plate. Garnish with fresh mint leaves. Serve right away.