- Preheat an oven to 400°F. Spread the bacon in a single layer on a rimmed baking sheet. Bake until the bacon is crisp and browned, about 20 minutes. Transfer the bacon to paper towels to drain. (Alternatively, fry the bacon on a griddle or in a large frying pan over medium heat until crisp.)
- Preheat the broiler. Arrange the bread slices on a baking sheet. Broil, turning once, until toasted on both sides, about 3 minutes. Transfer the bread to a work surface.
- Spread mayonnaise on one side of each bread slice. Halve, pit and peel the avocados. Place an avocado half, cut side down, on top of 4 of the bread slices. Slice the avocado directly on the bread, taking care not to cut into the bread, then fan out the slices. Season with salt and pepper. Top each avocado half with 3 bacon slices (cut to fit if necessary), 2 tomato slices and 1 lettuce leaf. Place 1 bread slice, mayonnaise side down, atop each lettuce leaf. Cut each sandwich in half and serve.
- TIP: These same sandwich ingredients can be transformed into a salad by using a little less bread and a little more lettuce. Cut 4 bread slices into cubes, coat with a drizzle of olive oil, and toast under the broiler to make croutons. Toss the sliced avocados and tomatoes, croutoons, torn lettuce and chopped bacon with your favorite vinaigrette (hold the mayo).