Boil water and revive the mushrooms by putting them in a capped container with the hot water. When they're revived, cut them into small strips.
Soften the bean thread noodles with some hot water.
Use the remaining hot water to blanch the mung bean sprouts.
Cut up the tofu into small (7mm square) cubes.
Mix all the ingredients in a large bowl, except for the wrappers. Optionally add a beaten egg to make it stick together better.
Make the dumplings: put a small quantity of this mixture in dumpling wrappers, and then pinch the sides together, sometimes a little cold water will help them stay stick together.
Boil a pot of water and throw small batches of the dumplings into the water. They're ready when they float. Scoop them out with a slotted spoon or strainer and then make another batch. Excess dumplings can be frozen.