Heat 1 tbsp olive oil in a large heavy pot over medium heat. Sauté half the sliced mushrooms until golden and tender, about 5 minutes. Season with salt and pepper and set aside. Repeat with another tbsp of oil and the rest of the mushrooms. Add the remaining oil, then sauté the diced onion, carrot and celery until soft, 7-8 minutes. Stir in garlic, thyme, paprika, onion powder, garlic powder and bay leaves, season, and cook 1 minute until fragrant. Add barley and lentils, then the stock. Cover and bring to a boil. Uncover and simmer until barley and lentils are tender, about 30 minutes, stirring now and then. Discard the bay leaves. Dissolve the miso in a ladle of hot broth and stir it back in. Add the mushrooms, non-dairy cream, sherry vinegar, Worcestershire and dill. Bring back to a boil and adjust the seasoning.

Notes:
I like the look and firmness of black Beluga lentils in this soup, but green lentils and French lentils will both substitute easily here.
White wine vinegar is a fine substitute for sherry vinegar. I would go down to 2 teaspoons to start though.
Miso and vegan Worcestershire sauce are both quite salty, so just be mindful of how much salt you’re adding leading up to the point when they go in.
For non-dairy cream, I like the nutpods brand original unsweetened creamer or Califia’s Better Half non-dairy cream. You could also use unsweetened cashew milk (I like Elmhurst brand) or oat milk.
I do not recommend substituting hulled barley as it will take twice as long to cook and you would need to delay adding the lentils. I also find that hulled barley does not “starch up” the soup as nicely.