Remove stems from mushrooms. Combine soy sauce, wine, sugar, sherry, onion, garlic, salt and ginger in a saucepan. Bring to a boil and remove from heat. Pour over mushrooms in a heatproof glass or stainless steel bowl, or in a canning jar.
Refrigerate for two days, turning mushrooms to coat with the marinade twice daily. Can be kept in refrigerator up to one week before serving.
Submitted by: CM