Add bacon to frying pan over medium high heat. Cook until crispy and remove to paper towel covered plate (try to keep as flat as you can). Reserve all of the grease in the pan.
Reduce heat to medium and add onions and Worcestershire sauce. Saute until onion are softened, approximately 10 minutes.
Combine mayo and garlic powder.
Toast each slice of bread.
To build the sandwich, smear one side of toast with garlic mayo, then layer up with four slices of bacon, one leaf of lettuce, 3-4 slices of avocado, two slices of tomato and a portion of onions. Smear garlic mayo on another slice of toast and place on top. Press down slightly and secure with long toothpicks.