Cook the Chicken: Add olive oil to your pan. Season chicken breasts with rosemary, salt and pepper. Cook the chicken breasts for six minutes on each side.
Make the Filling: Wash your lettuce several times, and then slice it up in order to reduce its mass. Add a generous amount of mayonnaise.
Butter the Bread: Butter the sliced bread on one side only and toast on the buttered side. Arrange and serve your sandwich.