Wash and wipe down the mangoes without any moisture. Cut each mango in half, remove the seed and cut each half into 3-4 pieces.
Repeat this with all the mangoes, roughly making about 4-5 cups of cut mangoes.
In a big air tight container, add red chilli powder, mustard powder, salt and turmeric powder.
Mix it well and add methi/fenugreek seeds and black chana (if adding) along with garlic pods.
Now add cut mango slices to the spice powders.
Toss around in such a way that each mango piece is coated in the spice powder.
Add about 1/4 cup of sesame oil and mix it all well.
The mixture should be wet but not dripping in oil. Now close it tightly and set it to rest for a couple of days.
Open the container after two days, mix around and add all the oil. Let the pickle rest again for a couple of days in the closed container.
After 2-4 days, the pickle is ready to use. Top with more oil as needed, as it acts as a preservative. Store in glass containers or porcelain pots that are tightly wrapped with cloth. Store in a dry but cool place for shelf life upto a year.
Serve avakaya pickle with hot rice, ghee and mudha pappu!