Step 1

Bring the sake and mirin to a boil in a medium saucepan over high heat. Boil for 20 seconds to evaporate the alcohol. Turn the heat down to low, add the miso paste, and whisk. When the miso has dissolved completely, turn the heat up to high again and add the sugar, whisking constantly to ensure that the sugar doesn't burn on the bottom of the pan. Remove from heat once the sugar is fully dissolved. Cool to room temperature.

Step 2

Pat the salmon fillets thoroughly dry with paper towels. Slather the fish with the miso marinade and place in a non-reactive dish or bowl and cover tightly with plastic wrap. Leave to marinate in the refrigerator for at least 3 hours and up to 3 days.

Step 3

Preheat oven to 425°F. Line a baking sheet with aluminum foil. Lightly wipe off any excess miso clinging to the fillets, but don't rinse it off. Place the fish skin-side-down on the pan and transfer to the oven and cook for 8 minutes, then turn the oven to broil and broil for 3-4 minutes until the top of golden/black in spots and is opaque in the center and flakes easily. Flake fish into pieces and pile on top of the noodles. Garnish and serve.

Step 4

Combine the ginger, garlic, and two-thirds of scallions together in a large bowl.

Step 5

Heat the oil in a small saucepan over medium high heat for about 2 minutes. Turn the heat off and add the ginger mixture. Let the mixture infuse for 5 minutes before stirring in remaining scallions. Stir in soy sauce, rice wine vinegar, pepper, sesame oil, and sugar; season with salt. Set aside for 15 minutes to let flavors come together. Taste and adjust seasonings.

Step 6

Meanwhile, cook noodles according to package directions. Drain and toss with as much or as little scallion sauce as you'd like in bowl. Top with flakes of salmon and assorted garnishes.