Season the salmon with salt and pepper. Let sit for 10 minutes, then lightly dredge in cornflour.
Heat a large frying pan with 1 tablespoon oil over high heat. Sear the salmon, then reduce the heat to medium-low. Continue to cook until the salmon is 90% done, about 5-6 minutes total. Transfer to a serving dish and sprinkle with sesame seeds.
Heat the same frying pan with 1 tablespoon oil over high heat. Stir in the white miso paste, water, mirin, Japanese soy sauce, sake, ginger juice, sesame oil and cornflour slurry. Stir and simmer until the sauce has thickened, about 2-3 minutes. Pour over the salmon and garnish with seaweed.
White miso paste, mirin, tamari and sake can be purchased in Oriental speciality stores.
Ginger juice - finely chop fresh ginger or blitz in a food processor. Place the chopped ginger into a cloth and squeeze out the juice.