Fry the bacon until crispy and then drain on paper towel. Toast the bread and then spread one side of each slice with mayonnaise. Divide and top one side of 4 of the mayonnaise spread bread slices with lettuce, tomato, avocado and bacon. Set on the remaining bread slices, mayonnaise side down. Slice each sandwich into halves or quarters and serve.
Recipe Options: For spicy-tasting sandwiches, add pinches of ground cumin and cayenne pepper to the mayonnaise before spreading on the bread. For a more colourful sandwich, instead of leaf lettuce, use the colourful mixed baby greens in these sandwiches.