In a large steamer pot, bring 3 inches of water to a boil over high heat. Meanwhile, mix the scallions and ginger in a small bowl. Scatter a third of the mixture in the center of a piece of foil large enough to wrap the 4 fish pieces. Place the fish pieces side by side on top. Season with salt, pepper and half of the remaining ginger mixture. Make a sealed packet. Steam until cooked, 10 minutes. Discard the ginger and scallion.
Meanwhile, cook the noodles according to package directions, about 6 minutes; drain and rinse. In a large nonstick skillet, heat 1 tbsp. oil over medium heat. Add the garlic and cook until fragrant, about 1 minute. Increase the heat and stir in the broccoli rabe; season with the crushed red pepper, salt and black pepper. Cover and cook, 1 to 2 minutes. Add the noodles; toss.
In a small skillet, heat the remaining oil over medium-high heat. Add the remaining ginger mixture and cook for 10 seconds. Spoon the ginger sauce over the fish along with the soy sauce. Serve with the noodles.