Stack wonton wrappers and cut each into 3–4 triangles. To fry: heat 1 inch of neutral oil in a heavy skillet to 350°F (175°C). Fry triangles in small batches, turning once, until golden and crisp, about 30–45 seconds per side. Transfer to a paper-towel-lined tray and season immediately with 1/2 tsp fine salt. To bake (lighter): preheat oven to 400°F (200°C), lightly brush or spray both sides of triangles with oil, arrange single layer on a baking sheet, bake 6–8 minutes until golden and crisp, flipping halfway; season with salt.

Make Spicy Mayo Dressing

In a small bowl combine 3 tbsp Japanese mayonnaise, 1 tbsp Sriracha, 1 tsp sesame oil, 1 tsp fresh lime juice, 1/2 tsp soy sauce and 1/2 tsp honey or mirin. Whisk until smooth and emulsified. Taste and adjust heat or acidity as desired. Reserve 1 tbsp of this sauce for drizzling on the finished tartare.

Prepare Tartare Base

Keep fish cold. If using both salmon and tuna, combine equal parts so total is 8 oz. If using only one, use 8 oz of that fish. Pat the fish dry with paper towels and finely dice into roughly 1/4-inch pieces. Place diced fish in a chilled bowl.

Add 2 tbsp finely minced red onion, 2 tbsp thinly sliced scallion, 2 tbsp seeded diced cucumber and (if using) 1/2 cup diced avocado and 1 tbsp chopped cilantro to the bowl with the fish. Gently fold to combine without smashing the fish.

Add 1 tsp rice vinegar, 1 tsp toasted sesame seeds, 1 tsp furikake or chopped nori (optional), 1/4 tsp freshly ground black pepper and up to 1 tsp fine sea salt (start with 1/2 tsp). Toss gently and taste; adjust salt or lime juice if needed.

Fold in about 2 tbsp of the prepared spicy mayo—reserve 1 tbsp for drizzling—until the fish is evenly coated but still loose and glossy. Do not overdress; the mixture should remain slightly chunky.

Plate and Finish

Using a ring mold (2–3 inch) or spoon, portion the tartare onto chilled small plates or a shared platter. Press gently to shape if using a ring, then lift straight up to release. Alternatively serve spooned into small bowls.

Drizzle 1–2 tbsp eel sauce in a swoop across or around the tartare. Drizzle the reserved 1 tbsp spicy mayo decoratively over the top. Sprinkle remaining toasted sesame seeds and a pinch of furikake or chopped nori. Garnish with microgreens or cilantro sprigs and a small mound of pickled ginger if desired.

Arrange wonton chips around the tartare. Serve immediately so the chips stay crisp. Provide extra eel sauce and spicy mayo on the side if desired.