01 - In a large mixing bowl, gently combine the ground turkey, finely minced onion, minced garlic, finely chopped fresh parsley, Worcestershire sauce, Dijon mustard, kosher salt, and freshly ground black pepper. Mix thoroughly but avoid overworking the meat, as this can lead to dry burgers.
02 - Divide the prepared turkey mixture into four equal portions. Carefully shape each portion into a patty, ensuring they are slightly larger in diameter than your chosen hamburger buns to account for shrinkage during cooking.
03 - Heat 1 tablespoon of olive oil in a large skillet or grill pan over medium heat until shimmering.
04 - Place the formed turkey patties in the hot skillet. Cook for 5 to 6 minutes per side, or until they are golden brown and an internal temperature of 165°F (74°C) is reached.
05 - During the final minute of cooking, place one slice of cheddar cheese on top of each turkey patty. Cover the skillet to help the cheese melt evenly and become gooey.
06 - While the patties are cooking, lightly toast the hamburger buns to your preference, either in a separate pan, toaster, or under a broiler.
07 - To assemble, place a large lettuce leaf on the bottom half of each toasted bun. Top with a turkey patty adorned with melted cheese, followed by a slice of ripe tomato and a thin slice of red onion. If desired, spread mayonnaise or ketchup on the bun halves. Cap each burger with the top bun.
08 - Serve the turkey burgers hot and enjoy.