Cut the green tomatoes into quarters, and each quarter into half. You can cut them smaller if you prefer. Add the chilli powder and salt and mix well. Keep aside.

Now heat the oil in a wok. Add the mustard seeds and when they splutter, turn down the heat to medium. Add the asafetida powder and curry leaves and stir once ensuring they don't burn. Immediately add the tomato pieces. Stir well and allow the tomatoes to cook for about 5 minutes. They should soften without losing the skin or becoming mushy.

Add the fenugreek powder and jaggery and mix well. Allow to cook for another minute or so and take off the heat.

Allow to cool, bottle and refrigerate when not using. This pickle will keep in the fridge for a week. If kept outside, it will spoil as the water content of the pickle is on the higher side.