1 bunch scallions; whites cut into ¼ inch pieces, greens cut into 2 inch pieces
1 tablespoon minced peeled ginger
1 tablespoon low sodium soy sauce
½ teaspoon sugar
Kosher salt and ground black pepper
4 ounces shitake mushrooms, stemmed, and sliced ¼ cup cornstarch
2 plum tomatoes, cored, cut into large chunks
12 ounces firm white fish (pollock) cut into 1 inch pieces
6 ounces bay scallops
2 tablespoons balsamic vinegar
Heat the vegetable oil in a large pot over medium-high heat. Add the scallion whites and cook until slightly tender, 2 to 3 minutes. Stir in the ginger and cook about 1 minute. Add 7 cups water, the soy sauce, sugar, salt to taste, ¾ teaspoon pepper and the mushrooms. Cover and bring the broth to a simmer. Mix the cornstarch with ¼ cup cold water and gradually stir into the broth. Bring to a gentle boil, stirring; the broth will thicken slightly.
Add the scallion greens, tomatoes and white fish to the broth, and simmer until the fish is opaque, about 3 minutes. Add the scallops, vinegar, and salt and pepper to ta(the scallops will cook instantly from the heat of the soup). ladle into bowls.