Place a wire rack in the bottom of a roasting pan and add an inch of water to the pan. Place pan on the stove over two burners and bring water to a boil.
Meanwhile, rinse and dry the fish inside and out. Place on a heat-safe platter and stuff the cavity with half the ginger, scallions, and chile pepper, all the garlic, and 4 sprigs mint. Season with 1/4 teaspoon salt. Top fish with remaining ginger, scallions, and chile pepper, and season with 1/4 teaspoon salt.
Transfer platter to prepared
pan. Cover tightly with foil and steam
until opaque throughout, about
15 minutes. Carefully lift platter
from pan, retaining the juices.
Meanwhile, combine lime juice and oil in a medium-size bowl. Season with 1/4 teaspoon salt and pepper to taste, and add remaining mint and the basil leaves. Toss to coat the herbs.
Place herb mixture on top of the fish and serve immediately.