Chef's notes: I truly love soup – it tends to be healthier, usually contains several vegetables and provides a soothing, easy to digest meal in a bowl. Definitely make the porcini part of this soup – it can seem like an expensive ingredient but a little goes a long way and the flavor profile it adds is amazing! The timing on this soup is a bit longer so think of it as a lazy weekend treat rather than a quick mid-week meal. It is worth the wait! (those with an Instant Pot can definitely speed up the cooking time- the barley cooking phase can reduce to 20 minutes)
In a small bowl, add porcini mushrooms to 1 cup of warm water; set aside for 5 minutes. In a separate bowl, add shiitake mushrooms to 1 cup of warm water; set aside for 5 minutes. Reserving the liquids, drain and dice the mushrooms.
In a medium pot on medium heat, drizzle in the oil. Sauté the onion with the thyme and garlic until just translucent; add the stock, the water from the dried mushrooms and the barley. Turn up the heat to medium high, the liquid should remain at a gentle bubbling simmer. Cook the barley for 1 hour; as it cooks keep scraping the bottom of the pot to keep the barley grains from sticking. Add additional water to keep the soup loose, if needed. Once the barley is really soft and puffy, add the carrots, celery, and sliced mushrooms; simmer 20 minutes longer. Season to taste with black pepper and garlic salt and finish with the parsley.
Serve with some crusty bread topped and toasted with Gruyère or Swiss cheese for a gooey, savory side or opt for light salad greens tossed with olive oil, fresh squeezed lemon and some shaved Parmesan cheese.