Heat grill pan or large skillet over high heat.
Place the tuna in a food processor and pulse until the fish is coarsely chopped.
In a large bowl, mix together the tuna, garlic, scallions, ginger, Dijon mustard, cilantro, coarse black pepper, and sesame oil. Chill for one hour, to allow the flavors to blend.
Divide the mix into four, evenly-sized burgers, season with salt and drizzle with olive oil. Place the tuna burgers in a very hot grill pan or skillet and cook for two minutes on each side until it has a golden brown crust on the outside, but is still rare to medium-rare inside. Take care not to overcook the tuna. Hold the cooked patties on a plate under foil.
Heat a grill pan or skillet with olive oil. When hot add the eggplant slices and cook for 3 to 4 minutes on each side until soft and golden in color. Season to taste and keep warm.
To make the Soy Wasabi Mayonnaise, mix together the mayonnaise, wasabi paste, lime juice, soy sauce, cilantro, salt and pepper until well combined.
Toast the buns. Cover the bottom halves with some salad leaves, and two slices of grilled eggplant. Cover with one slice tomato and followed by the tuna burgers. Finally, top each burger with wasabi mayonnaise, close the bun and serve.