Take 1 piece of onion (medium size), 1 piece of green capsicum (large size), 1 piece of yellow capsicum (medium size), and 1 piece of red capsicum (medium size) on a chopping board. Chop them all finely and keep them aside on a plate. (Pro tip: You can use different vegetables of your choice as well such as finely chopped carrots, cabbage, and others. Remove the seeds and white portion of the capsicum along with it while cutting).

Now, heat a frying pan on medium flame and melt half a cube of butter and remove the other half to use later. (Pro tip: If you do not have butter due to health reasons, you can use white oil to fry the vegetables. However, butter or ghee enhances the taste and flavor of the vegetable stuffing).

Put the chopped vegetables in the hot butter.

Stir the vegetables continuously to cook them nicely on a high flame for more than a minute to remove the raw smell and moisture from them. Fry until they change color and become dry. When it does, add ½ tsp of salt, ½ tsp of chili flakes, ½ tsp of oregano, and ¼ tsp of black pepper (crushed) to it. Mix them nicely and cook for a minute or so.

Switch off the flame of your gas stove and transfer the cooked vegetables to a separate bowl to cool down a bit. (Pro tip: Cooling the cooked vegetables is crucial as heat may cause the mayonnaise added to melt and impact the consistency of the vegetable stuffing).

Now, add 3 tbsp of mayonnaise. (Pro tip: Do not put too much mayonnaise even if you like it a lot as it will make the stuffing moist which will come out while grilling. Use hung curd if you do not have mayonnaise).

Mix it nicely with the vegetables to make a thick and dry stuffing as shown in the image below.

Now, put 2 pieces of lettuce leaves on only two of the bread slices as shown in the image below.

Then, gently and carefully spread the vegetable stuffing to cover the lettuce leaves entirely.

On top of the vegetable stuffing, put 50 gm of paneer (cut in large thin slices) just as shown in the figure below. (Pro tip: If you want you can use a single slice of paneer. You may even grill the paneer slightly before putting it on the bread slices).

Now, cover each bread piece with a slice of cheese.

Put the other slice of bread on top of the cheese slice. Apply butter on the outer surface of this bread slice as shown in the image below.

Now, heat a sandwich grill and grease it with a little bit of butter.

Place the sandwiches on it and apply butter on the top surface of the bread slices as shown in the image below. Let it cook slowly for a minute or so on a medium flame. (Pro tip: Frying the sandwich on a medium or low flame will help achieve the desired crunchiness).

Flip the sandwiches carefully one by one when one side of them is done. (Pro tip: Do not worry about frying or the doneness of the vegetable stuffing as it is already cooked and therefore will not taste raw or uncooked).

Flip them a couple of times to achieve the lovely design of small rectangles as shown in the image below and crunchy golden-brown crust on the exterior of the bread slices.

Remove them from the grill onto the chopping board and cut them diagonally with a sharp knife very carefully from the center and move outward. (Pro tip: Do not press the sandwiches too much while cutting as that will squeeze out the stuffing from inside).

Your homemade tasty and crunchy vegetable paneer grilled sandwich is ready to eat. Serve them hot.