In a large bowl, combine the ground turkey, panko, egg, Worcestershire sauce, 1 tablespoon ketchup, 1 tablespoon Dijon, dried parsley, garlic powder, onion powder, and 1 tablespoon olive oil. Season with kosher salt and black pepper. Mix gently with your hands until just combined, being careful not to overwork the meat.

Divide the mixture into 4 equal portions and shape each into a patty about 3/4 inch thick. Press a slight indent in the center of each patty to prevent puffing during cooking.

Heat a cast iron grill pan or heavy skillet over medium heat. Lightly brush the pan with a little olive oil. Place the patties in the pan in a single layer (cook in batches if needed). Cook for 3-4 minutes per side, or until the internal temperature reaches 165°F on an instant-read thermometer.

To assemble, spread mayonnaise on the bottom half of each bun. Top with a lettuce leaf, then the cooked burger. Add a generous smear of smashed avocado, a drizzle of ketchup and mustard, and a few slices of tomato and red onion. Close with the bun top and serve immediately.