Wash and wipe green chilies well, then chop into roundels. or make thin slices as per your choice
Peel and make thin slices of the ginger.
Put them in a glass bottle or jar and add salt, turmeric and mustard powder(rai) and keep covered for 4 hours.
Then add lemon juice, oil and fennel seeds. Mix well.
Let it mature for 2 -3 days and then start consuming. (You may start using it immediately after making it, but the taste gets enhanced after 2-3 days).
Keep at room temperature for 1 week. Then keep refrigerated for 2-3 months (Keep mixing OR shaking the bottle every once a while).
you can also add fresh turmeric slices (kachi haldi/or amba haldi) into it along with ginger.