Place chillies in a bowl of water with a large pinch of salt and turmeric powder. Wash thoroughly to remove all dirt, then strain and drain excess water through a colander.
2
Spread a clean cloth on a large tray and lay chillies on it. Pat dry with the cloth to remove all moisture. Either sun-dry or use a fan for 10-15 minutes until completely dry—any remaining moisture will shorten shelf life.
3
Once dry, remove the top of each chilli and cut lengthwise in half, then halve again to create thin strips. Apply oil to hands or wear gloves if you have sensitive skin.
4
Transfer cut chillies to a clean, completely dry bowl. All utensils and vessels used from this point onward must be completely dry.
5
Add mustard seeds to a spice grinder and grind until fine powder forms. Transfer to a clean bowl.
6
Add fennel seeds to the grinder and pulse until coarsely ground, leaving some pieces crushed and some coarse. Transfer to the same bowl.
7
Add ground mustard, coarsely ground fennel, Kashmiri red chilli powder, turmeric, salt, methi kuria, and mustard oil to the bowl. Mix well until uniform.
8
Add the prepared masala to the cut chillies and mix thoroughly so every piece is evenly coated.
9
Heat 2 tbsp mustard oil in a pan until hot, add asafoetida and let it sizzle, then pour the hot oil directly over the masala-coated chillies. Mix immediately so the tempering coats everything evenly.
10
Transfer the pickle into a clean, dry airtight glass jar. Pour 25-50 ml mustard oil over the top to completely cover the pickle. Give a final mix.
11
The spicy, tangy Mirch Ka Achaar is ready. Serve with laccha paratha or alongside any meal.