01 - In a large bowl, combine ground turkey, breadcrumbs, egg, red onion, garlic, Worcestershire sauce, salt, and pepper. Mix gently until just combined; do not overmix to maintain tenderness.
02 - Divide the mixture into 4 equal portions and shape into patties about 1/2 inch thick. Make a slight indentation in the center of each patty to prevent puffing during cooking.
03 - Preheat a grill or skillet over medium-high heat. Lightly oil the surface to prevent sticking.
04 - Cook the patties for 5-6 minutes per side, or until fully cooked. The internal temperature should reach 165°F for safe consumption.
05 - In the last minute of cooking, place a slice of Swiss cheese on each patty. Cover the grill or skillet to melt the cheese completely.
06 - Toast the burger buns cut side down until golden and crispy, approximately 1-2 minutes.
07 - Spread mayonnaise and/or mustard on the toasted buns according to preference.
08 - Layer lettuce on the bottom bun, followed by the turkey patty with melted cheese, avocado slices, and tomato. Top with the remaining bun halves.
09 - Serve the burgers immediately while hot and enjoy.