Heat 2 tbsp oil in nonstick skillet. Fry the paneer sticks till light golden color. Remove them from pan and keep them immersed in warm water.
Heat remaining oil in the same skillet. Add cumin seeds, kalonji, green chilies and red chili flakes. Sauté till cumin turns golden on low heat.
Increase heat to medium and add onions and stir fry till just translucent on high heat. Keep stirring.
Add capsicums and sauté for 2 minutes.
Add tomatoes and sauté till tomatoes wilt. Add ginger and sauté well. Add vinegar and ketchup. Stir and mix.
Add red chili powder, turmeric powder, and salt to taste. Cook till oil separates and masala looks glazy. Finally add paneer and toss to let masala coat the paneer.
Cook for another minute or so. Switch off gas. Remove to a serving bowl and serve with paratha/roti.