In a bowl, combine yogurt, tandoori masala, red chili powder, ginger-garlic paste, lemon juice, salt, and vegetable oil. Mix well to make a marinate.

Add the paneer slices or cubes to the marinade and coat them evenly. Allow the paneer to marinate for at least 30 minutes. The longer you marinate, the more flavorful the paneer will be

Heat a non-stick skillet or grill pan over medium heat. Brush it lightly with oil

Cook the marinated paneer on the skillet until it's well-cooked and has grill marks, typically 2-3 minutes per side.

For Assembling the Sandwich:
Toast the slices of bread in a toaster or on a griddle with a little butter or ghee until they are golden brown

Optionally, spread some mint chutney or tamarind chutney on one side of each slice of bread

Place the grilled tandoori paneer slices on one slice of bread.

Add slices of onion, tomato, and cucumber on top of the paneer

Top with another slice of bread, chutney side down

You can serve the sandwich as is or grill it on a griddle with a bit of butter or ghee on both sides for a few minutes until the cheese melts and the sandwich is toasted to your liking