To make the sauce, in a small bowl, mix 1 cup water, soy sauce, hoisin sauce, ginger, scallions, and garlic, and set aside.
Cook the noodles, but cook them 1-2 minutes less than the packet instructions, as they will keep cooking in the sauce.
While the noodles are cooking, heat a a wok over high heat. Add 2 tablespoons of vegetable oil and heat until shimmering.
Add the shrimp and stir-fry for 2-3 minutes, until just cooked. Remove the shrimp to a bowl.
Add the remaining 2 teaspoons of vegetable oil and stir-fry the scallions for 30 seconds, until fragrant. Add the red pepper and stir-fry for 1 minute, then add the shrimp and the sauce. Stir together.
By now the noodles should be ready, so drain and add to the wok. Toss to combine everything well. Remove from the wok and serve immediately.
