Rinse porcini mushrooms with water, then place in a small, heatproof bowl. Cover with 1 ½ cups boiling water.
When mushrooms have softened, remove them from the bowl, squeezing any liquid that clings to them back into the bowl (save this soaking liquid). Rinse mushrooms well to remove any grit. Squeeze water out of mushrooms (discarding it), then roughly chop the mushrooms.
Place fine mesh strainer over over a small bowl. Pour mushroom soaking liquid through strainer. Set liquid and mushrooms aside until ready to use.
While mushrooms are soaking, heat olive oil in a large soup pot or dutch oven over medium heat.
When oil is hot, add onions, carrots, and celery. Season with salt, then saute until onions start to turn translucent, about 5 to 7 minutes.
Turn heat up to medium-high, then add mushrooms. Saute, stirring often, until mushrooms are tender and any liquid they release has evaporated (about 10 minutes).
Stir in garlic and thyme, and season veggies with more salt. Cook, stirring constantly, until garlic is fragrant (about 30 seconds).
Add broth, barley, bay leaves, reserved porcini mushrooms, and mushroom soaking liquid to pot. Bring soup to a boil, then reduce heat to a simmer.
Cook soup uncovered until barley is tender, about 30 to 40 minutes. Stir in parsley, then season to taste with salt and pepper.
Serve soup hot. Enjoy!
Notes
Make sure to read the info before this recipe card for tips, serving suggestions, and more!