OK, I usually make this in large quantities, but I'll reduce the recipe just for you:
2 cups of green mango ( preferably not too green - they must be fully developed and just about to ripen)
1 heaped teaspoon of salt.
1/2 teaspoon of Hing (Asafoetida) - you can buy it in just about any Asian shop. It smells really stinky, but it's sold as a diluted white powder. (The neat ingredient is brown and smells positively evil.) Two good things about hing - it adds a nice undertone, and it prevents flatulence. It's made from a herb. (They call it the devil's dung because of its smell

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- about 1/2 teaspoons of fenugreek powder, or better about 12 fenugreek seeds .
1 tablespoon of coarsely ground mustard seeds. You can use a mixture of yellow and black mustard or add some halves if you like.
1/2 a teaspoon of dried turmeric powder or about 1 centimetre of root turmeric finely chopped
2 tablespoons of red chilli powder.
4 tablespoon of oil - use mustard oil if you can get it. (it sometimes says on the bottle - for external use only, but I use it internally in the kitchen as well as for barbecues.

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Directions:
Wash the mangoes and cut them into small cubes. You might have to wear gloves if you are sensitive to green mango. Mix in the chilli powder, hing and salt well and leave it to stand (overnight is cool)
Heat about a tablespoon of oil in a small wok or tadkah pan (Spelling?).
Fry the fenugreek seeds until the fragrance is obvious (don't burn) then crush in a mortar and pestle.
put then aside.
Fry the mustard seeds and turmeric and put it aside.
After an hour transfer all your spices and hing together into the mango mixture.
Be careful with the fenugreek. You might like to add half first and taste it. Too much can make it bitter. The salt can also be added to taste. Some like it salty.
This pickle or chutney is excellent as a side condiment with curry. It's also nice to add raita as another condiment.