Start by preparing the shrimp. Use kitchen shears to trim away the legs and sharp edges around the head. Cut the shrimp open along the back, and de-vein (a toothpick can help). Rinse, shake off excess water, and set aside.
Next, prepare the sauce. Add the minced garlic and chilies (if using) to a medium heat-proof bowl. Heat the oil in a pan until it shimmers, and carefully pour the hot oil evenly onto the garlic and chilies (it should sizzle). Then stir in the light soy sauce, oyster sauce, Shaoxing wine, sugar, and salt.
In a medium, wide pot (preferably a clay pot), layer the ingredients in the following order: red onion, napa cabbage, enoki mushroom, and mung bean vermicelli noodles. Then arrange the shrimp on top in a circular pattern. Pour the water evenly over the shrimp, followed by the prepared sauce mixture. Cover the pot.
Put the pot on the stove over medium-high heat. Cook for 12-15 minutes, or just until the shrimp turn opaque. (Cooking time will vary depending on the size of the shrimp. I had very large shrimp—10-12 shrimp per pound—so I cooked them for 15 minutes.)
Uncover, garnish with chopped scallion, and serve immediately.
Video
Notes
To prepare in advance, layer all the ingredients in the pot (except the water and sauce). Refrigerate for up to 1 day. When ready to cook, take it out of the refrigerator. If you have a traditional clay pot, let it come close to room temperature, as extreme temperature changes can crack the pot. Prepare the sauce, pour the water and sauce over the ingredients in the pot, and put on the stove. Cook as instructed. If you're not using a traditional clay pot and you're taking the pot directly from refrigerator to stove, it may take a minute or two longer to cook—13-16 minutes.