1. Bring a large saucepan of water to a boil. In a large bowl, cover the mung bean noodles with warm water and let stand until pliable, about 5 minutes. Drain the noodles and cut them into 4-inch lengths. Boil the noodles until tender but still chewy, about 25 seconds. Drain and return the noodles to the pot. Rinse twice under cold water and drain; let stand in the colander.
2. Season the shrimp with salt, white pepper and 1/2 teaspoon of the Sichuan peppercorns. In a large, deep skillet, heat 1 tablespoon of the vegetable oil until shimmering. Add the shrimp and cook over moderately high heat, turning once, until pink on the outside and white within, about 2 minutes. Transfer the shrimp to a plate.
3. Add the remaining 2 tablespoons of vegetable oil to the skillet and heat until shimmering. Stir in the scallions and ginger and cook until fragrant, about 1 minute. Stir in the mung bean noodles, soy sauce, vinegar, chile oil and the remaining 1/2 teaspoon of Sichuan peppercorns and cook until heated through, about 1 minute. Add the shrimp and season with salt and white pepper. Transfer to shallow bowls and serve right away.