Wash and wipe chilies. Dry thoroughly.
Slit each chili length wise.
Slightly roast the saunf and methi seeds on tawa (griddle) and coarsely grind it along with rai and kalonji.
Heat 2 tablespoon of mustard oil to smoking point. Cool and mix with the ground spices and salt.
Stuff this mixture into the chillies and place them in a clean bottle. Top with any remaining mixture.
Pour rest of the oil on the top.
Keep the pickle in a warm place for 2-3 days.