Heat oil or butter in a pan and add cumin seeds.
Once they splutter, add onions and sauté until translucent.
Stir in bell peppers, garlic, and ginger. Cook for 2-3 minutes.
Add paneer, turmeric, chili powder, and salt. Mix well and cook for 3-4 minutes.
Remove from heat and stir in fresh cilantro if using.
Spread the mixture between slices of bread.
Toast the sandwiches with butter or oil until golden and crisp on both sides.
Serve hot with ketchup, chutney, or your favorite dip.