Combine onion, vinegar and salt in a bowl and keep aside.
Paneer Filling
Add oil to pan or kadai on medium heat. Once the oil is hot, add garlic and ginger and sauté till fragrant. Add onion and green chilli and sauté till onions are translucent. Add capsicum and sauté for a minute.
Add soy sauce, vinegar, ketchup and chilli sauce. Stir to combine. Add paneer and stir to combine. Sauté for 2-3 minutes or until the paneer is soft and tender. Ensure the sauce coats the paneer and vegetables. Add a teaspoon of water if it is sticking to the pan.
Assemble
Spread some of the pickled onion on a hot paratha in the middle. Add some of the prepared paneer filling on top of it. Sprinkle some fried noodles. Roll tightly from one end securing the filling inside. Serve hot along with some ketchup or mint chutney.