I first had these at a great little restaurant in Portland called the Boke Bowl. On my second trip I knew I had to come up with a way to make them at home. Here's my version.These are delicious on their own, but we love them as a condiment to Asian rice or noodle dishes. Try to find dried mushrooms that are already sliced, to save some time and effort.The prep time here includes soaking time. Pictures to come.
Pour boiling water over mushrooms in a medium bowl.Water should fully cover the mushrooms.Cover with a small plate that will keep the mushrooms under the water. Soak 1-1 1/2 hours until soft and pliable. Drain, reserving about 1 cup of the soaking water. Squeeze mushrooms gently to remove excess moisture (they do not need to by "dry").
Combine mushrooms and remaining ingredients, except green onion, if using, in a medium saucepan. Add just enough of the reserved mushroom water to cover, as needed.(about 1/2 cup)
Bring mixture to a boil. Reduce heat and simmer about 20-30 minutes until mushrooms are very dark and soft. Adjust vinegar and soy sauce as needed. They should be a little sweet/sour and a little salty.
Remove from heat. Sprinkle with finely chopped green onion, if desired. Remove the ginger piece. Cool. Refrigerate in tightly sealed container. These will keep well in the fridge for about 2 weeks.
Serve over rice bowls or noodles. They are also delicious in scrambled eggs or tofu.