01 - Combine ground turkey, red onion, garlic, Worcestershire sauce, smoked paprika, salt, and black pepper in a mixing bowl. Mix until just combined without overworking.
02 - Divide the mixture into 4 equal portions and shape into patties approximately 1/2 inch thick.
03 - Preheat grill or skillet over medium-high heat and lightly oil the surface.
04 - Cook patties for 5 to 6 minutes per side until internal temperature reaches 165°F.
05 - During the last minute of cooking, place a slice of Swiss cheese on each patty and cover to melt.
06 - Toast burger buns cut side down until lightly golden.
07 - If desired, spread mayonnaise or Greek yogurt and Dijon mustard on the bottom buns. Layer lettuce, turkey patty with melted cheese, avocado slices, tomato, and sprouts. Cap with the top bun.
08 - Serve immediately while warm.