How to Make It
In a small nonreactive saucepan, bring the soy sauce, mirin and sake to a boil over moderately high heat. Cook until reduced to 1/3 cup, about 4 minutes. Transfer to a bowl and let cool completely, then add the sesame oil, 1 tablespoon of the olive oil, the ginger, garlic, cayenne and black pepper. Let the sauce stand at room temperature for at least 2 hours or refrigerate overnight.
Using a very sharp knife, slice the tuna 1/3 inch thick. Cut each slice into 1/3-inch-thick matchsticks and then finely chop the tuna; work quickly so that the tuna stays cold. Transfer the chopped tuna to a bowl and refrigerate until chilled again.
Meanwhile, heat the remaining 1 teaspoon of olive oil in a small skillet. Add the pine nuts and stir over moderately high heat until lightly toasted, 4 to 5 minutes. Transfer to a paper towel-lined plate and rub to remove the oil. Coarsely chop the pine nuts and put them in a small bowl. Add the sesame seeds to the skillet and toast over moderately high heat, stirring constantly, until golden, 2 to 3 minutes. Add to the pine nuts.
Peel and finely dice the apple. In a bowl, combine the tuna, pine nuts, sesame seeds, apple, cucumber and scallions. Stir the sauce and add 1/2 cup to the tuna. Toss quickly and thoroughly. Spoon the tartare onto 8 chilled plates and sprinkle with the avocado and nori. Set a quail egg yolk in the center of each serving and drizzle a little of the sauce around the plates. Serve immediately.