In a wok or a large frying pan, sauté the mushrooms, onion, bok coy, and cabbage in the 1/2 cup water for 5 minutes.
Add the sprouts, tofu, soy sauce, sesame oil, and ginger. Simmer for 10 minutes. Add the cornstarch mixture. Cook, stirring, until thickened. Set aside and let cool.
Place one eggroll wrapper on the counter like a diamond. (Cover the remaining wrappers with a damp cloth to prevent them from drying out.) Take about 1 heaping tbsp of filling and squeeze out the excess liquid. Spread the filling on the lower third of the wrapper. Starting at the point closest to you, bring the bottom half of the wrapper up to enclose the filling. Fold in the two sides and continue rolling up the dumpling. Brush a little water over the inside of the tip and press the edges together.
Line a steamer basket with parchment paper or lettuce or cabbage leaves to keep the dumplings from sticking. Set the filled dumplings in the basket over boiling water. Cover and steam for 10 minutes, or until the wrappers are translucent.