Place a skillet (I use 10 inch skillet) over low medium heat. You could use enamaled cast iron, non stick or stainless steel skillet.
Add butter & oil to the skillet and let warm up. Add chopped onions and green chilies. Sauté for a few minutes until the onions turn translucent. Don't brown too much.
To the onions add the garlic paste, diced bell pepper and frozen corn. Saute for 2-3 minutes on low medium heat until the vegetables soften a little bit. Don't cook through.
Stir in the chopped tomatoes and cook them until they release their juices and become soft. Don't dry out the tomatoes- this will keep your paneer filling saucy and we very much desire that.
Mix in the paneer cubes (drain it if you soaked in hot water) and sprinkle the salt, black pepper & pav bhaji masala. Squeeze the lime juice. Cook for 1-2 minutes or until the paneer is warmed through and soft. Check and adjust the seasonings as needed. Make sure that the filling doesn't dry out too much.
Switch off the heat and mix in the chopped cilantro. Your paneer mixture is ready. Once cooled down, you can refrigerate it for later use or let's make paneer sanwiches next!
Lightly spread soft butter or oil one side of a bread slice.
Place a generous amount of the paneer stuffing onto the slice of bread. Top it with some shredded cheese (optional).Cover with another slice of bread.
Carefully transfer the sandwich to the skillet, buttered side down. Cook over medium heat until the bottom side is golden brown and crisp, about 2-3 minutes. Spread butter or oil on the side facing up.
Using a spatula, gently flip the sandwich and cook the other side until it turns golden brown and crisp, and the paneer filling is heated through.
Once both sides are toasted to your liking and the filling is hot, remove the sandwich from the skillet. I transfer toasted sandwiches onto a wire rack immediately so that the bottoms dont become soggy.
Repeat the toasting process with the remaining sandwiches.
You could sprinkle some bhujia (crispy gram flour noodles on top). Slice the sandwiches into two halves and serve hot with cilantro chutney, tomato ketchup or your favorite dipping sauce. Don't forget the masala chai!