
Preheat oven to 400˚F. Place bacon on a foil-lined baking sheet in a single layer. Bake 15 to 20 minutes or until browned and crisp then transfer to a paper towel-lined plate to cool.
In a small bowl, combine sauce ingredients and set aside.
Lightly butter both sides of the toast and toast on a dry griddle or skillet over medium-high heat just until golden brown.
Arrange 4 slices of bread on a cutting board and spread 1 Tbsp of sauce over each toast. Add lettuce then tomato, bacon, avocado. Sprinkle salt and pepper over the avocado.
Spread 1 Tbsp sauce over the remaining toasted bread and place over the sandwich, sauce side down. Cut in half if desired and serve.