Drain canned crabmeat and gently flake with a fork, removing any cartilage or shell fragments. Pat crabmeat lightly with paper towels to remove excess moisture. Finely chop raw prawns into small pieces (about 1/4-inch); pat dry.

Mix aromatics and binder

In a large bowl combine minced shallot, minced garlic, chopped parsley, chives, lemon zest, lemon juice, Dijon mustard and 3 tablespoons mayonnaise. Stir until combined.

Combine seafood and season

Add crabmeat and chopped prawns to the bowl with aromatics. Sprinkle in Old Bay seasoning, salt and black pepper. Gently fold to combine without overworking to keep texture delicate.

Bind and form patties

Add beaten egg and 3/4 cup of the panko breadcrumbs to the seafood mixture and fold gently. If mixture feels too wet, add remaining panko up to the full cup until it holds together when pressed. Divide mixture into 4 equal portions (about 4 oz each) and shape into patties roughly 3.5 inches wide and 3/4 inch thick. Chill patties in the fridge for 15 minutes to firm them.

Cook patties

Heat a large nonstick or cast-iron skillet over medium heat. Add 2 tablespoons butter or oil and let heat until shimmering. Place chilled patties in skillet (do not overcrowd). Cook 3–4 minutes per side until golden brown and internal temperature reaches 145°F (63°C) and prawns are opaque; press gently once after flipping to ensure contact. If patties brown too quickly, reduce heat to medium-low and finish cooking for an additional 2–3 minutes. Transfer cooked patties to a plate and keep warm tented loosely with foil.

Zesty Mayo

While patties chill or cook, whisk together 1/2 cup mayonnaise, 1 tablespoon lemon juice, 1/2 teaspoon lemon zest, 1/2 teaspoon hot sauce (or 1/2 tsp cayenne), 1/2 teaspoon Dijon mustard and 1/2 teaspoon honey (or sugar). Season with 1/4 teaspoon salt and 1/4 teaspoon black pepper. Taste and adjust acidity or spice. Refrigerate until assembly.

Assembly & Toppings

Toast buns: Butter the cut sides of the 4 buns lightly and toast in a clean skillet or under a broiler until golden, about 1–2 minutes.

Assemble burgers: Spread about 1 heaping tablespoon of zesty mayo on the bottom half of each toasted bun. Place a lettuce leaf on the mayo, then a slice of tomato and a few thin rings of red onion if using. Top with a warm crab & prawn patty, add another small dollop of mayo to the patty if desired, then crown with the top bun.

Serve: Serve immediately with lemon wedges on the side for squeezing over the patties. Optional sides: fries, salad or coleslaw.