Double Yellowfin Tuna & Swordfish Belly Bacon Cheeseburger Recipe

Prepare fish

Keep the yellowfin tuna and swordfish belly very cold. Trim any sinew. Finely chop both fish separately on a chilled board, then combine in a large bowl so the mix totals about 16 oz (10 oz tuna + 6 oz swordfish belly).

Build mixture

Add the grated cold butter, minced shallot, chopped chives, beaten egg white, and panko breadcrumbs to the chopped fish. Season with 1 tsp kosher salt and 1 tsp freshly ground black pepper. Mix gently with a fork or your hands just until combined — avoid overworking to keep texture tender.

Form patties

Divide the mixture into four equal portions (about 4 oz each). Using lightly oiled hands, form each portion into a 3 1/2-inch wide, 3/4-inch thick patty. Press a small shallow indentation in the center of each patty with your thumb (this helps even cooking). Transfer patties to a plate, cover, and chill in the refrigerator for 15–20 minutes to firm up.

Sear patties

Heat a heavy skillet or cast-iron pan over medium-high heat until shimmering. Add 1 tbsp neutral oil and swirl. Sear the patties 2–3 minutes on the first side without moving them, until a golden crust forms. Flip and cook another 1–2 minutes until just opaque and cooked through but still moist (target internal temp ~120–130°F / 49–54°C for medium-rare to medium for tuna). Remove patties to a warm plate. If using a thermometer, avoid overcooking—the swordfish belly has fat that tolerates slightly more heat but tuna can dry out.

Cook swordfish belly 'bacon'

In the same skillet over medium heat, lay the swordfish belly bacon slices in a single layer. Cook 2–4 minutes per side until edges crisp and fat renders (timing depends on thickness). You want a tender, slightly crisp bacon-like texture. Transfer to paper towels to drain.

Melt cheese over patties

Return the seared fish patties to the pan on low heat (or place on an ovenproof tray under a broiler on low). Stack half the cooked swordfish bacon over two patties and top each with a 1 oz slice of sharp cheddar. Cover the pan with a lid for 30–60 seconds or place briefly under the broiler until the cheese just melts and begins to bubble. Remove and keep warm.

Prepare sauce

In a small bowl, combine 4 tbsp mayonnaise, 2 tsp Dijon mustard, 1 tsp lemon juice and chopped capers (if using). Taste and adjust seasoning. This tangy mayo complements the fatty swordfish belly and tuna.

Toast buns & assemble greens

Butter the cut sides of 4 brioche buns lightly. In a clean skillet over medium heat, toast the buns cut-side down until golden, 1–2 minutes. Lay lettuce leaves on bottom buns, place a tomato slice on top of the lettuce, or reserve tomato for top if preferred.

Assemble burgers: Spread about 1 tbsp of the prepared mayo-mustard sauce on both cut sides of each toasted bun. Place a lettuce leaf and tomato slice on the bottom bun, then set a melted-cheese fish patty on top. Add a second patty (if making a double-stacked burger) or the remaining plain patty to create a double layer — for this recipe, stack two patties per burger to achieve the “double” in the title (if you prefer single, use one patty). Top the top patty with additional swordfish belly bacon slices. Finish with a sprinkle of 1/8 tsp coarse sea salt and a pinch of black pepper across the patties.

Serve immediately with lemon wedge: Offer lemon wedges to squeeze lightly over the assembled burger (the acid brightens the rich fish). Serve remaining bacon on the side or tuck onto the top bun. Enjoy hot.