Wash, clean, and cut sour/tart mangoes into small pieces, removing the seed or hard center portion.
Keep the diced mangoes aside.
Add all the coarse powder ingredients (likely spices like fennel, mustard, fenugreek, etc.) into a blender jar and make a coarse spice powder, being careful not to over-blend.
In a mixing bowl, combine the diced mangoes, prepared coarse spice powder, Kashmiri chili powder, turmeric, and salt. Mix well and set aside.
Heat mustard oil in a small tempering pan. Once hot enough, add asafoetida (hing) and immediately pour the hot oil over the mango mixture.
Mix thoroughly and allow to cool completely. Your instant mango pickle is now ready!
Once cooled, store the pickle in a glass or ceramic jar for up to 1 month. Refrigerate after 3-4 days.