Add tomatoes to a food processor. Pulse until well-chopped.
Fenugreek, coriander, cumin, and fennel seeds should be added to a spice grinder and ground coarsely.
Take out in a bowl and combine with chaat masala, salt, garam masala powder, citric acid, turmeric powder, red chili powder, coriander powder, and powdered Kashmiri red chilies.
Reserve half of the mixture in a bowl for later use.
Add lemon juice and mustard oil to the remaining spice mixture and stir thoroughly.
Slit green peppers along the middle, remove the seeds, and fill with the prepared spice mixture.
Add cooking oil, and onion, and sauté in the pot until lightly golden.
Add the garlic and ginger and combine.
Add the saved spice mixture along with the pureed tomatoes and mix well. Cover and simmer on low heat until the oil separates (8-10 minutes).
Add the chicken, stir well, and simmer for 10 to 12 minutes at a medium temperature.
Add water, stir well, and then bring it to a boil.
Add fresh coriander and filled green chilies. Cover and simmer for 12 to 15 minutes at a medium temperature.
Add lemon juice, thoroughly combine, and cook on high heat until oil separates.