Add water to the dried shiitake mushrooms and let them soak for about 1 hour, until they are softened. Drain, pat dry, and finely dice.
Toss the peeled and deveined shrimp with baking soda and a pinch of salt. Let it sit for 10 minutes. Rinse thoroughly and pat dry, then chop into small, fine pieces.
In a large bowl, combine the ground pork, chopped shrimp, diced shiitake mushrooms, soy sauce, oyster sauce, Shaoxing wine, sugar, white pepper, MSG, and cornstarch. Mix well until fully combined.
Place a wonton wrapper on your palm.
Spoon about 1 tablespoon of filling into the center and spread it out.
Use your thumb and index finger to shape and “O.” Use this to hold the shumai.
Carefully create gentle pleats with a spatula or your fingers.
Stand the shaped shumai upright on a parchment-lined tray.
Cover with a damp towel to prevent drying while you assemble the rest.
Steam the shumai in a bamboo steamer or a pot with a steaming rack for 8–10 minutes, until the filling is fully cooked and the wrappers are tender.
Pair with soy sauce, chili oil, or your favorite dipping sauce.