How to Make It
In a small saucepan, bring the soy sauce, rice vinegar, sugar and 3 tablespoons of water to a boil. In a small bowl, whisk the kudzu with 1 tablespoon of water, then whisk into the saucepan. Boil over moderately high heat until thickened, about 1 minute. Remove from the heat and whisk in the sesame oil, sesame seeds, yuzu kosho and 2 tablespoons of the canola oil; keep warm.
In a bowl, toss the mochi with the furikake. Season the snapper with salt. In a large nonstick skillet, heat 1/4 cup of the canola oil. Using a 1/3 cup measuring cup, scoop 3 loose mounds of the mochi mixture into the skillet; flatten them slightly. Set 1 fillet on each mound. Spread another 1/3 cup of the mochi on each fillet. Cook over moderately high heat until golden, about 4 minutes. Using a spatula, carefully flip the fish and cook until golden and the fish is cooked through, 4 to 6 minutes. Drain on paper towels. Wipe out the skillet and repeat with the remaining 1/4 cup canola oil, mochi mixture and fish. Transfer the fish to plates and garnish with scallions. Serve with somen noodles and the sauce.