In a large bowl mix together mangoes with salt and pickle masala and set aside for two hours.
Heat oil in a non-stick pan. Add mustard seeds and saute till it splutters.
Remove and set aside to cool.Add it to the the mango and mix well. Cover it and set aside.
Heat sugar with two and half cups water in a deep non-stick pan and cook till the syrup thickens.
Remove and allow to cool. Add it to the mango mixture and mix well.
Keep it in the sunlight for two hours daily for five days.
The pickle is ready to serve.