01 - In a large bowl, gently combine ground turkey, finely chopped onion, minced garlic, Worcestershire sauce, Dijon mustard, salt, and black pepper until just mixed.
02 - Divide the mixture into four equal portions and shape each into a patty approximately ¾ inch thick.
03 - Heat olive oil in a skillet or grill pan over medium heat. Cook the patties for 5 to 6 minutes per side, ensuring an internal temperature of 165°F is reached.
04 - During the last minute of cooking, place a slice of Swiss cheese atop each patty and cover the pan to melt the cheese.
05 - Lightly toast the whole wheat burger buns to preference.
06 - On the bottom bun, spread mayonnaise and/or ketchup if desired. Layer with romaine lettuce, the turkey patty with melted Swiss cheese, tomato slices, avocado slices, and optionally red onion. Top with the bun lid.
07 - Serve immediately alongside preferred sides.