Add the besan flour to the mustard oil. Mix well to form a paste.
Switch on the stove and sautee this until bubbles are formed. This step is important as it removes the raw taste of the gram flour and enhances its nutty flavor.
In a mixing bowl, combine curd, turmeric powder, chilli powder, coriander powder, cumin powder, dry mango powder, garam masala, ginger garlic paste, salt, and juice from half a lemon and the mustard oil and gram flour mixture. Mix well to create a smooth marinade.
Cut the paneer, onion, capsicum, tomato, and bell peppers into bite-sized pieces.
Add the paneer and chopped vegetables to the marinade. Coat them evenly with the mixture.
Let the mixture marinate for at least 30 minutes. Longer marination time will enhance the flavors.
Heat oil in a pan. Once the oil is hot, spread the marinated paneer and vegetables on the pan. Cook until the paneer and vegetables are cooked and have a nice char on the surface. Turn them occasionally to ensure even cooking. Once done, remove from heat and set aside.