In a vessel add 1.5 cup of water, salt and let it boil. When it starts boiling add gooseberry/amla pieces. Lower the flame and cook the amlas till water reduces to half(approximately 3/4 cup). Let this cool.
Dry roast the mustard seeds and fenugreek seeds till mustard seeds splutter. Remove them and in the same pan add oil and roast the red chillies.
Add roasted red chillies, mustard seeds and fenugreek seeds in to mixer grinder. Grind it to paste by adding water used in cooking gooseberries in steps.
Now add this paste to cooked, cooled gooseberry/amla pieces. Mix well.
Now in seasoning pan, add 2 tbsp of oil, mustard seeds and asafoetida. When mustard seeds splutter, switch off the flame. Allow the seasoning to cool then add it to amla pickle.
Store it in a airtight container. After a day you can start using it.