Wash the irumban puli (bilimbi) in running water, and dry with a cloth.
Slice them lengthwise into four pieces, season with salt, mix well and spread them on a plate.
Note: Don't use steel or other metal plates. The acidity will discolour the plate.
Keep the plate in sunlight to dry the salted bilimbi.
If you are in a hurry, skip the sun-drying and pickle directly. In that case, skip the next 3 steps.
You'll notice the colour of the irumban puli (bilimbi) changing to light green/yellow.
The salt and the heat from the sunlight will start to dry the bilimbi slices. Keep it covered overnight.
Next day, keep the plate in sunlight again.
Roast the fenugreek seeds and the ural dal in a pan.
Switch off when they start to turn brown, allow it to cool, and powder it and keep it aside.
Heat gingelly oil in a pan, and splutter some mustard seeds.
Lower the flame, add the powdered mixture, chili powder, turmeric powder and asafoetida.
Slowly stir for a minute and turn off the flame. Ensure that you don't burn this mix.
Add curry leaves and the sun-dried irumban puli, mix well until they get a good coat of the masala mix.
Once the pickle has cooled down, transfer to a clean, dry bottle.
Drizzle the pickle with some more gingelly oil on the top, and keep the bottle in the fridge.
You can start using the pickle after 3-4 days. If you can't wait, just for it!