Step 1Fill the bottom of a steamer (or a roasting pan fitted with a rack) with at least half an inch of water and bring to a boil. Cut the ginger into shreds by slicing it lengthwise into thin sheets; stack the sheets and slice lengthwise. Scatter half the ginger on a heat-proof plate or platter large enough to hold the whole fish.
Step 2Trim the dry ends of the green onion tops and then cut about 3 inches of green tops. Shred these lengthwise as thinly as possible. You should have about one-fourth cup of shredded green onion tops. Scatter half of the shredded onion tops over the ginger.
Step 3Lightly season the fish inside and out with salt and place it on the plate. Scatter the remaining ginger and green onion over the fish. Place the plate on the steamer rack and cover tightly. Cook until a knife easily penetrates the flesh and the top fillet begins to lift easily, 6 to 10 minutes depending on the size of the fish.
Step 4With the steamer still in place, drizzle soy sauce over the fish, mound pea shoots on top and drizzle with sesame oil. Cover and cook until pea shoots have barely wilted, about 1 minute. Remove steamer from the heat and let the fish stand, covered, for a few minutes before serving.