To begin, remove the sticks from the soya chaap and cut them into 1" pieces.
Marinate with salt, Kashmiri red chilli powder, and lemon juice. Mix well and keep aside for at least an hour.
Heat mustard oil to the smoking point. Turn off the heat and let it cool.
Heat the oil again. Deep fry the chaap pieces on medium heat until they are golden. Remove and keep aside.
In the same oil, add in the coarsely ground ginger first because it takes time to cook. Then add in the coarsely ground garlic. Cook for a minute.
Next, add in the coarsely ground onion. When it starts to change color. Add in the dry masalas. Do not brown.
Add in cumin powder and coriander powder. Mix well.
Next, add in Kashmiri red chilli powder and salt. Remember you have already added the salt and chillies to the marinade.
Add in white vinegar.
Next, add in the fried chaap pieces and mix until well coated.
Finally, add in garam masala powder and kasoori methi. Mix well.
The Achari Soya Chaap is ready to serve. Although it is ready to eat, let the achar stand for a hour or so so that the chaap pieces absorb the masalas. Serve with puris or paranthas.