Wash and dry the chicken breasts. Sprinkle salt and pepper to taste on your chicken, both front and back.
Heat some olive oil and balsamic vinegar in a skillet and cook the chicken for 5-8 minutes on each side. The chicken breast must remain juicy. Remove from heat, cover and let stand for 10 minutes.
In the meantime, combine ricotta and basil leaves. Season with pepper.
Toast the 8 slices of rye bread and spread equal amounts of ricotta cheese on 4 of the 8 slices.
Once it has cooled down, cut the chicken breast into thin slices. Do the same with the strawberries, blackberries (cut in two) and the avocado. Place the chicken breasts, avocado, blackberries and strawberries on the sandwich. Top with lettuce leaves and close your sandwich with the remaining slices of toasted bread.