Heat oil in a pan. Add ginger-garlic paste and sauté on low flame for a few seconds. Add all the vegetables except onions (and paneer if required) and coriander leaves. Add salt, chilli, coriander, garam masala and chat masala powder. Sauté till the raw smell is gone. Mix atta, salt, few drops of oil and warm water to make chappathi dough. Roll into chappathis and cook both sides. Place the vegetable mixture in the middle of each chappathi, along with the sliced onions. Roll tightly and wrap with butter paper/ foil if required. Serve hot with ketchup.