Crackle mustard seeds without oil. keep it aside.
Dry roast fenugreek seeds and keep it aside.
heat oil, fry urad dal and chana dal until it is brown. keep it aside.
Grind/finely powder together all these.
Heat sesame oil. Once it is lukewarm, add in the ground masala, turmeric powder and chilli powder. mix well.Add salt and asafoetida and mix well.
Add grated mangoes and remaining oil (if required heat up some more oil and add to it when luke warm so that mangoes get soaked in )mix well and let it rest on counter for a day. Refrigerate and use for a couple of weeks.