Heat up the frying pan over medium heat. Lay out the bread and dry on both sides for 30 seconds. Transfer to a plate. Add bacon to skillet and cook for 2 minutes. from each side. Remove from pan.
Cut the fillet in half lengthwise into 2 thin cutlets. Add salt and pepper to taste. Put in the pan where the bacon was fried, and fry for 3-4 minutes. on each side until done.
While the fillet is fried, cut the tomato into thin slices. Grease 2 pieces of bread out of 4 with mayonnaise. Arrange lettuce leaves, fried bacon slices, and tomato slices on bread. Add chicken fillet and cover with remaining bread.