Divide the chicken fillets so they become half as thin.
Cut the mushrooms, onion, cucumber and mozzarella cheese in thin slices.
Place the chicken fillets and the hamburger breads on the grill. If you use a frying pan, place the hamburger bread in a toaster.
When the breads are done place them on a plate and prepare all the ingredients except the mozzarella cheese on the lower part of the bread.
When the chicken fillets are almost done place two mozzarella cheese slices on each fillet so the cheese melts a bit.
To enhance the flavor you can use some oregano on top of the mozzarella cheese.