Stir in the sliced mushrooms and season with salt and pepper. Allow the mixture to cook until the mushrooms soften, which takes about 5 to 8 minutes.
Next, pour the chicken broth into the pot. Rinse the pearl barley under cold water and add it to the pot along with the bay leaves.
Bring the soup to a rolling boil, then lower the heat and let it simmer until the barley becomes tender, roughly 40 to 50 minutes. Ladle into bowls, serve warm, and savor the flavors!