To begin, de-seed, peel, and dice the papaya into bite-sized pieces.
Heat mustard oil in a pan to the smoking point and let it cool a bit. Add mustard seeds (sarson), fenugreek seeds (methi dana), fennel seeds (saunf), nigella seeds (kalonji), and asafoetida (hing). Allow them to splutter.
Add in finely chopped onions and green chillies. Saute until the onions are translucent.
Add in the diced papaya. Mix well.
Next, add in the dry masalas - salt, black salt (kala namak), black pepper powder, Kashmiri red chili powder, and cumin powder (jeera). Saute. Add a bit of water if required, cover with a lid, and cook until the papaya soften a bit.
Next, add in brown sugar and white vinegar. Cook until the sugar melts, the liquid dries up a bit, and oil starts appearing on the sides.
Finish with crushed green cardamoms and garam masala powder. Mix well.
The Sweet & Spicy Papaya Chutney is ready to serve. Enjoy with puris or parathas.