1. Mix the soy sauce, sake, mirin, ginger, garlic, chile flakes, and sugar
in a medium bowl. Place the salmon fillets in a sturdy freezer bag.
Pour about the marinade into the freezer bag with the fish. Seal the
freezer bag and place in a baking dish (so that if the bag leaks it
doesn't get all over your fridge). Place in your refrigerator and chill
at least 2 hours, preferably overnight.
2. A) Grilling method
Brush the grill grates with olive oil; pre-heat your grill to medium
heat. Remove salmon from bag, reserving the marinade. Place salmon
either directly on the grill grate, or on a piece of aluminum foil
(brushed with olive oil) over the grill grate, skin side down. Brush
frequently with the marinade glaze, cook the salmon 10-20 minutes
(depending on thickness of the fillets), until easily flaked with a
fork.
3. B) Pan frying method
Heat a few tablespoons of olive oil in a skillet over medium-high heat.
Drain the salmon and reserve the marinade. Fry the salmon 4 to 5
minutes per side, basting frequently with the marinade. Serve once the
salmon is cooked through and is easily flaked with a fork.
4. C) Baking method
Preheat oven to 350°F. Line a baking dish with aluminum foil. Brush the
top of the foil with olive oil. Drain the salmon and reserve the
marinade. Place salmon on the foil, skin side down. Bake for 10-20
minutes depending on how thick the fillets are, basting frequently with
the marinade, until the salmon is easily flaked with a fork.
5. If you have some remaining marinade, you can heat it in a small
saucepan until simmering. Remove from heat and pour into a small gravy
boat for serving with the salmon. This is optional.