Asian-style flounder packets

2 large green onions
2 tablespoons soy sauce
2 tablespoons seasoned rice vinegar
2 teaspoons grated, peeled gingerroot
Total Time: 18 minutes

1.Cut tops of green onions crosswise into 2-inch pieces, then cut each piece lengthwise into thin strips; reserve for garnish. Thinly slice white part of green onions.
2.In small bowl, mix soy sauce and rice vinegar.
3.Preheat oven to 425 degrees F. From roll of foil or cooking parchment, cut four 15" by 12" sheets.
4.Arrange 1 flounder fillet on half of each piece of foil; spread each with 1/2 teaspoon ginger. Spoon 1 tablespoon soy-sauce mixture over each flounder fillet; top with sliced green onions. Fold other half of foil over fish. To create sealed packets, fold edges of foil over about 1/2 inch all around, overlapping folds. Place packets in 15 1/2" by 10 1/2" jelly-roll pan. Bake packets 8 minutes.
5.To serve, with kitchen shears, cut an X in top of each packet to let steam escape before serving. (When packets are open, check that fish flakes easily when tested with a fork.) Garnish fish with reserved green-onion strips.