Add minced green chilli and ginger and sauté for 10 seconds.
Add onion and sauté till it turns translucent.
Now add all the dry powders like red chili powder, coriander powder, turmeric powder, cumin powder, garam masala powder, salt and mix well. The mixture will look dry now.
Add crumpled or grated paneer, coriander leaves and mix well till it gets combined well with the onion mixture. Take off stove and let the mixture cool down a bit.
Paneer filling is ready for the sandwich.
Grease one side of all the bread slices with butter.
On the ungreased side of all bread slices, drop ½ tbsp of tomato ketchup and spread well.
Place required amount of the paneer filling, say 2-3 tbsp on top of the tomato ketchup and spread evenly.
Close with another bread slice with the greased tomato ketchup side facing the filling and the buttered side facing the top.
Make another sandwich following the same procedure.
Heat the sandwich maker with the grill plates as mentioned in the manual of your brand.
Place the assembled sandwiches on the hot grill plates and grill till evenly browned.
Release the knob and open the lid, gently remove the grilled paneer sandwiches on to a serving plate.
If you do not have a sandwich maker, heat a tawa or skilled, grease with either oil or butter and place the assembled sandwich and cook over low flame till the bottom side is evenly browned. Gently press the top with a spatula while cooking so that the sandwich sticks together.
Gently flip the sandwich so that the other side gets cooked and browned too. Transfer to a serving plate.
Cut the sandwich across using a sharp knife into triangles and serve piping hot with tomato ketchup.
My kids do not like tomatoes in their sandwich filling as they go mushy, so I smear tomato ketchup on the bread slices to make it tangy.