Using a sharp chef's knife cut mangoes into half. Then cut each half into 1-inch cubes along with the hard inside pit. Discard the innermost seed that will fall out.
Add the cut mango pieces to a bowl and sprinkle salt and turmeric. Mix well and keep covered overnight. This helps remove some sourness from the mango pieces and helps release the excess moisture. Turmeric makes the pieces firm preventing the mango pieces from getting soft so that the pickle has a nice bite to it. The antibacterial turmeric also helps with extend the shelf life of the pickle
The next morning, pour the mango pieces into a strainer to drain out all of the liquids.
Keep the drained mangoes in a single layer on an old kitchen towel for 8 hours to dry out the excess liquids. This step will further increase the shelf life. Just remember to use an old kitchen towel as it will get stained from the turmeric and you will most probably end up discarding the towel.
Heat oil in a medium skillet. Add mustard seeds and allow them to pop. Add asafetida. Turn the heat off and allow the oil to cool completely. Add jaggery to the oil and give a quick stir.
Add mango pieces to the oil along with the pickle masala and salt. Mix well.
Using disposable gloves add the pickles to a clean and dry glass jar, pressing the pickle firmly inside the jar.
Cover the jar with a cheesecloth or paper towel and secure it with a rubber band. Keep overnight. Keep in an airy spot. By morning some of the excess oil will start to rise to the top. Mix well again and keep covered with the cheesecloth. Repeat this step for 3 to 4 days
Pickle will be ready to enjoy in 3 days. You can then close the lid and keep it in a cool dry place. You can also refrigetare the jar if you like.
If you like more pickle masala to enjoy with rice, khichdi or chapatis add the entire package of pickle masala and an additional ¼ cup of oil.