01 - Combine ground turkey, red onion, garlic, Worcestershire sauce, smoked paprika, salt, and black pepper in a mixing bowl. Mix gently until just incorporated to avoid a dense texture.
02 - Divide the mixture into four equal portions and shape each into a patty approximately 1/2 inch thick.
03 - Heat a grill or skillet over medium-high heat and lightly oil the surface to prevent sticking.
04 - Place patties on the cooking surface and cook for 5 to 6 minutes per side, or until the internal temperature reaches 165°F.
05 - During the final minute of cooking, top each patty with a slice of Swiss cheese and cover to allow it to melt.
06 - Toast the burger buns cut-side down until lightly golden and crisp.
07 - Spread mayonnaise or Greek yogurt and Dijon mustard on the bottom buns if using. Layer lettuce leaves, turkey patty with melted cheese, avocado slices, tomato slices, and sprouts. Cap with the top buns.
08 - Serve the assembled burgers immediately for optimal freshness and flavor.