Wash nicely the mangoes and cut into small pieces as required.
Take mango pieces in glass bowl and add turmeric powder and salt, mix it nicely with mango pieces and then cover with a cloth or cling film and keep it aside for 7-8 hours. After that you will see, mango pieces will leave water.
Meanwhile wash the chickpea pieces and then dry these on a kitchen towel.
Squeeze out the water from mango pieces, keep in a separate glass container and refrigerate it.
Soak Chickpeas in Magno turmeric water overnight or for next 7-8 hrs. Chickpeas will absorb water and become soft after the soaking time.
Now take out the mango bowl from the refrigerator. You can dry it on a kitchen towel for 1-2 hrs or leave on the counter till it comes to room temperature. Then mix chickpeas and mango pieces together.
Meanwhile dry roast the fennel seeds, methi dana. The traditional recipe has fenugreek powder/methi dana powder also but since I did not have it I skipped it. If you have fenugreek powder you can use 1 tbsp of it..
Mix all the spices together, and add to mango and chickpea bowl.
Heat a pan on high flame for a minute. Switch off the flame, and add mustard oil to it, it will give smoke we call it cooking the oil(Tel Ka pakna). Let it cool down a bit, and add it to the mango bowl with all the spices. Do not add very hot oil.
Mix everything very well, coating all the mango pieces with spices and oil. Once the pickle comes down to room temperature, transfer it into a sterilized jar and with lid and keep it out in sun for 7-8 days.
Once the pickle is ready, just enjoy it with your favourite paranthe, dal chawal, pooris, theplas and mathris.