Begin by preparing the noodles. Submerge the dried rice noodles in hot water—just below boiling temperature—and allow them to soak for 15 to 20 minutes. The goal is to soften them until they’re flexible but still slightly firm in the center. Drain thoroughly and set aside. A light coating of oil will keep them from clumping.
Next, prepare the sauce. In a small bowl, blend together the soy sauce, oyster sauce, fish sauce (if using), sugar, white pepper, and broth or water. Whisk until the sugar dissolves and the mixture is smooth. If you’d like a slightly thicker sauce, stir together the cornstarch and water in a separate small bowl to create a slurry. Set both mixtures aside.
In a large wok or deep skillet, heat 1 tablespoon of oil over medium-high heat until shimmering. Add the shrimp in a single layer. Cook for about 1 to 2 minutes per side, or just until they curl, turn opaque, and develop a light sear. Remove the shrimp promptly and keep them warm.
Add another 1 to 2 tablespoons of oil to the pan. Stir in the minced garlic and ginger. Stir-fry for around 30 seconds or until fragrant. Immediately follow with firmer vegetables like carrots, onions, and bell peppers. Sauté for 2 to 3 minutes to allow them to soften slightly without losing their bite.
Toss in the bok choy and shredded cabbage. Stir-fry for an additional 1 to 2 minutes until the greens start to wilt and the colors remain vibrant.
Now add the drained noodles into the wok. Pour the pre-mixed sauce over the top. Using tongs or wide spatulas, gently toss the noodles and vegetables together until evenly coated. Continue stir-frying for another 2 to 3 minutes, allowing the noodles to absorb the flavors.
If you're using the cornstarch slurry, stir it quickly once more and drizzle it into the wok while tossing the noodles. Let it simmer for a minute until the sauce thickens slightly and clings to the noodles and vegetables.
Finally, return the shrimp to the wok. Stir everything together just long enough to reheat the shrimp and coat them in the sauce—about 1 minute.
Remove the wok from the heat. Garnish with fresh cilantro or sliced green onions if desired. Serve immediately while everything is piping hot and perfectly glossy.