Place the chicken in a big stockpot with celery, carrots, onion, bay leaves, and parsley. Cover with water and season liberally with salt and pepper. Bring to a boil and then reduce heat and simmer for 3–4 hours. Skim off any scum or foam that rises to the top. Let the pot cool and transfer to the refrigerator overnight.

The next day, remove the chicken from the broth and transfer it to a bowl. Strain the stock through a sieve into a big bowl and discard the solids. Pick the chicken from the bones and discard the skin and carcass. Wipe out the stockpot and return it to the stovetop.

Once your stock is ready to go, prepare the soup. Heat the neutral oil in the stockpot over medium-high heat. Once hot, add the mushrooms and cook for 8–10 minutes. Add the onions, carrots, and celery and cook, stirring often, for an additional 8–10 minutes.

Add the dry thyme, garlic powder, and crushed red pepper and cook for 1 minute. Pour in the reserved stock and chicken meat. Add the barley and then bring to a boil and then reduce heat to medium-low. Simmer for 30–45 minutes. If needed, supplement the soup with a bit of water or storebought stock, but you likely won't need it!

Once the barley is tender, turn off the heat, taste the soup, and season to your preferences.

Ladle the soup into bowls and garnish with more freshly minced parsley, if you like. Enjoy!