This vegan mushroom barely soup is rich in umami. What's that you ask? It's that fifth taste that our tastebuds love and so will you.
Soak the dried mushrooms in the boiling water for about 15-20 minutes. Then drain them, reserving the water (don't throw it away) and chop the re-hydrated mushrooms into bite-sized pieces. Set the water and mushrooms aside.

Heat the olive oil in a large pan. Add the chopped onions and cook them on medium heat for 3-5 minutes until transparent. Add the chopped carrots and celery and cook the vegetables an additional 3-5 minutes. Remove them to a large pot.

Raise the heat under the pan to high and add the fresh mushrooms, in batches if there are too many to fit comfortably in a single layer. Cook them stirring occasionally, for 3-5 minutes until the mushrooms begin to render their water/juices. Remove the mushrooms and their water/juices to the pot.

Add the final tablespoon of oil to the pan. Once it is hot, add the barley and cook stirring frequently for 1-2 minutes. Then add the chopped dried (rehydrated) mushrooms and continue cooking for another 1 minute. Once the barley and rehydrated mushrooms are heated and a bit toasted, add them to the pot.
Add the bay leaf or leaves, the mushroom soaking water, and the 4 additional cups of water or stock to the pot. Bring the soup to a boil, lower the heat and cook for 20-30 minutes for pearl barley or double that time for hulled barley. Add more water if required. Add soy sauce and tomato paste. Taste, then add salt if necessary and a good dose of freshly ground pepper.
As noted in the post and in my previous post on the differences between the types of barley, both pearl and hulled barley expand when cooked. An alternative method of making this soup would be to cook the barley in the 4+ cups of water/broth separately from the soup. Then if you add the cooked barley on a bowl-by-bowl basis, you'll avoid having the leftover soup turn more stew-like as the barley sits in it. Of course, that means you have to refrigerate the leftover soup and barley separately.