01 - In a large bowl, combine ground turkey, onion, garlic, parsley, Dijon mustard, Worcestershire sauce, salt, and black pepper. Mix gently until just combined.
02 - Divide the mixture into 4 equal portions and shape each into a patty slightly larger than the buns.
03 - Heat olive oil in a large skillet or grill pan over medium heat.
04 - Cook the patties for 5 to 6 minutes per side until golden brown and cooked through, ensuring the internal temperature reaches 165°F.
05 - During the last minute of cooking, place a slice of Swiss cheese on each patty and cover with a lid to melt the cheese.
06 - Lightly toast the burger buns on the skillet or grill.
07 - Spread mayonnaise on the bottom half of each bun if using. Layer with lettuce, turkey patty with melted cheese, avocado slices, tomato, and red onion. Top with the remaining bun halves.
08 - Serve immediately with your preferred side dishes.