Wash the raw mangoes nicely 2 - 3 times in water. Wipe each mango with a clean and dry kitchen towel to remove excess water. Make sure no water or moisture traces remain in the mangoes.
Chop each mango into 4 - 5 equal size pieces. We use a traditional raw mango slicer for the purpose. But the same can be done with a sharp knife as well.
Combine the mangoes, turmeric powder, and 2 tablespoons of salt and toss well using your fingers. Place the mangoes on a muslin cloth, cover with another piece of muslin cloth, and place under the sun for a day.
After a day once mangoes have released water, in a large vessel add the raw mango, remaining salt, and achaar masala. Combine nicely so that each piece of mango is coated with the spice mixture.
Transfer the pickle to a clean, dry, and sterilized jar. Make sure no dirt particles or moisture content remain in the jar before transferring the pickle. Seal the opening of the jar with a muslin cloth and keep under the direct sun rays for two days.
Shake the jar in between once in a day. Keep the pickle jar indoor once the sun sets.
After two days, heat mustard oil in a pan till it reaches the smoking point. Turn off the heat. Allow the oil to cool down completely at room temperature.
Pour the mustard oil in the pickle jar and shake the jar to mix. Now seal the jar with a tight fitting lid.
Keep the sealed jar under the direct sun rays for a week. By then, the pickle is matured. The mango pickle has a tendency to turn more flavorsome and tender with time.
You can store mango pickle for a year at room temperature.
Serve Aam Ka Achaar with Indian main-course dishes.