Grate 200 grams of paneer and keep it aside.
In a mixing bowl, add the grated paneer, 1 finely chopped onion, 1 finely chopped green chili, 1/4 teaspoon red chili powder, 1/4 teaspoon garam masala, 1/4 teaspoon chaat masala, salt to taste, and 2 tablespoons of chopped coriander leaves. Mix well to combine all the ingredients.
Take 8 slices of bread and spread a thin layer of butter on one side of each slice.
Place a generous amount of paneer mixture on the buttered side of 4 bread slices, and cover them with the remaining 4 slices, buttered side facing down.
Heat a non-stick tawa or sandwich maker, and place the sandwiches on it. Cook on medium heat until both sides turn golden brown and crispy.
Once cooked, remove the sandwiches from the tawa or sandwich maker, and cut them into halves or quarters.