Soak mung bean vermicelli in cold water for about 12 minutes until they become pliable.
Drain then cut the noodles with scissors into shorter strands. Spread them evenly over a plate for steaming.
Prepare the shrimp
Use scissors to trim off the shrimp’s legs and the top part of their heads. Then, split the shrimp open along their backs, keeping the tails and heads intact (see photos and video for reference).
Arrange the shrimp over the vermicelli, with the split side facing up.
Make the sauce
Put minced garlic into a small bowl. Heat oil until it just starts to smoke, then pour it over the garlic.
Add light soy sauce, oyster sauce, Shaoxing rice wine, sugar, white pepper, and 1 tablespoon of water. Mix well.
Spoon the sauce over the split part of the shrimp, and spread any remaining sauce over the vermicelli.
Steam the dish
In a wok or a steamer that's big enough to hold the shrimp plate, bring about 2 cups (500ml) of water to a full boil.
Place the plate of shrimp on a steamer rack or inside a steamer basket (wear gloves to protect your hands from the hot steam). Cover with a lid and steam over medium heat for 5 minutes (see note 2).
Sprinkle chopped scallions over the dish then serve immediately.
Video
Notes
1. Although this dish typically calls for whole shrimp, you may use shelled shrimp as substitute. Large ones are preferable.2. The whole shrimp I use is about 4 inches (10 cm) long each. If your shrimp are smaller or the total quantity is less than specified in the recipe, reduce the steaming time accordingly. Once the shrimp turn pink and curl slightly, they are cooked. Overcooking will result in a tougher, drier texture.