Slice each foccacia bread horizontally into two. Slice cheese into four slices. Slice each chicken breast into two. Make a marinade of olive oil, parsley, salt and crushed peppercorns. Keep one fourth of marinade aside.
Marinate the cheese slices and chicken breasts, separately in the remaining marinade for an hour. Heat a grill or tawa. Pick the chicken breasts from the marinade and cook them over the grill/tawa, covered, till both sides are done.
Apply remaining marinade to the foccacia bread slices. Place the basil leaves on the base along with the tomato slices and marinated mozzarella cheese slice.
Place a piece of grilled chicken breast and cover with another slice of focaccia and serve.