To prepare vinaigrette, in a bowl, combine 1/4 cup of the rice wine vinegar, the stock, miso, and sugar. In a blender, combine the remaining 1/4 cup of rice wine vinegar, the egg yolks, peanut butter, ginger, garlic chile, and mustard and puree until smooth. With machine running, slowly add the vegetable oil until incorporated, and then slowly add sesame oil. Stir in the sesame seeds. If the mixture seems to thick, add water until the mixture can be poured. Add the blended mixture to the bowl and stir thoroughly. Refrigerate until needed.
For the ginger-scallion oil, place the ginger and scallions in a deep mixing bowl. In a small saucepan, heat the peanut oil until just smoking. Slowly pour the hot oil over the ginger and scallion, being very careful as the oil will rise up the sides of the bowl. Add the sesame oil. Season with salt. Keep refrigerated.
For the chile pepper water, in a blender combine the 1/3 cup of water, garlic, chiles, vinegar, ginger, and salt and puree until smooth. In a saucepan, bring the 1 1/4 cups water to a boil. Add the pureed mixture and return to a boil. Remove from the heat. When cool, transfer to an airtight container. Keep refrigerated.
For the basil oil: In a saucepan of boiling salted water, blanch the spinach for 5 seconds. Drain and transfer to an ice bath to cool. Drain again and transfer to a blender. Add the basil, lemon juice, chile pepper water, garlic and oil. Season with salt, place in a blender, and puree; do not over blend as the oil will lose its color. Strain through a very fine sieve or strainer so that the oil is clear and bright green. Store in a glass container in a cool, dark place.
For the slivered scallions, using the back part of a large, sharp knife flatten the green parts of the scallions. Cut very finely on a diagonal so that the slivers are about 1 inch long.
For the fish, in a saute pan over high heat, heat the peanut oil until hot. Season the onaga with salt and pepper. When the oil is almost smoking, sear the onaga for about 45 seconds on each side, or until brown. When cool, top the onaga with the ginger-scallion oil (including the solids it contains) and dust on 1 side with the panko. Transfer the onaga to a oven-proof skillet or roasting pan. In a preheated 350 degree oven, bake for 6 minutes, or until tender and cooked through. Meanwhile, in a saute pan over medium heat, melt the butter. Add the mushrooms and saute for 3 to 4 minutes, or until they soften and begin to brown. Add the corn and saute for 2 minutes longer, or until the corn is slightly tender. To serve, divide the Sauteed vegetables among individual plates. Pour 1/2 cup of the vinaigrette around the vegetables and drizzle the basil oil over the vinaigrette. Place the onaga on the vegetables and top with the scallions. Sprinkle the sesame seeds around the plate.
Recipe courtesy Chef Alan Wong, author "New Wave Luau Cookbook"