How to Make It
Heat a small saucepan over high 30 seconds. Add sake, and cook until reduced by half, about 1 minute.
Prepare an ice bath. Add 2/3 cup water, soy sauce, Fortified Soy Sauce, fish sauce, and 1 1/2 teaspoons sugar to saucepan, and bring to a gentle simmer over medium-high. Simmer 1 to 2 minutes, stirring occasionally. Cook, without stirring, until mixture is translucent amber in color, about 1 minute and 30 seconds. Plunge saucepan into ice bath to prevent additional reduction. Set soy broth aside. (Rewarm gently before serving.)
Stir together salt and remaining 2 tablespoons sugar in a small bowl. Sprinkle over fish fillets; refrigerate 15 minutes. Prepare a bamboo steamer over medium-low. (Make sure the water in the pot is gently boiling.)
Rinse fish under cold water and pat dry. Place each fillet on a piece of parchment paper; top evenly with ginger strips. Place fish on parchment paper in a single layer in steamer. Cover and steam until opaque, about 12 minutes. Meanwhile, heat canola oil in a small skillet over medium-high until just smoking.
Transfer fish to a wire rack set inside a large rimmed baking sheet; discard parchment paper. Top fillets evenly with scallions, reserving some for garnish. Spoon about 1/4 cup hot canola oil over each fillet. (You should hear sizzling and smell the scallions immediately. The scallions should keep their green color.)
To serve, place a scallion-topped fillet on each of 4 plates; garnish with coriander flowers and a few raw scallion strips. Pour about 1/4 cup warm soy broth around each fillet; drizzle each with 1 teaspoon Ginger-Scallion Oil.