Chop the mango into 15 mm chunks and place in a lidded glass jar. Add the sea salt and shake thoroughly. Place in the sun and leave for 7 days.
Removed the mango pieces and drain in a sieve. Leave overnight to dry.
Mix one teaspoon of mustard seeds with the cumin and fenugreek and dry roast in a cast iron pan. Keep aside to cool. Add a little oil to the pan and fry the chilis for about 3 minutes. Remove and allow to cool.
Add the mixed seeds and the chilies to a spice grinder and grind until very smooth.
Heat the olive oil in a wok and add the remainder of the mustard seeds. When they begin to pop, add the mango chunks and mix thoroughly.
Sprinkle over the ground spices and stir fry for about 5 minutes. Turn off the heat and allow to cool,.