This is a very hearty, but at the same time fresh, bright sandwich.
We beat off the chicken fillet on both sides with a meat mallet. Salt and pepper. Mix both types of flour on a large flat plate. Roll the chicken fillet in flour.
Heat vegetable oil in a frying pan. Fry the cutlet over medium heat until cooked through, about 4 minutes on each side.
Lightly dry the bun in a toaster, in a pan or on the grill, grease both halves with a mixture of mustard and mayonnaise. Put a lettuce leaf on one of the halves of the bun. Next, lay the warm chicken cutlet. Put a slice of tomato and sweet onion rings on the cutlet and close the sandwich.
Serve as a main dish for lunch or dinner. Enjoy your meal!