Heat the olive oil in a large pot over medium heat. Once hot, add the onion, celery, and carrots. Cook, stirring often, until vegetables are softened, about 5 minutes. Add the minced garlic and continue to cook for another minute or two, or until the garlic is fragrant but not browned.

Carefully pour the broth and water into the pot. Add the bay leaf, dried thyme, salt and black pepper, if using. Stir to combine all the ingredients.

Bring the soup to a boil, then turn the heat down to a low simmer. Add the barley, cover the pot, and continue to simmer until the barley is cooked through, about 20 to 30 minutes.

Once barley is almost tender, add the peas for the last 2 minutes of cooking. Turn off the heat, remove the bay leaf, and let the soup cool for several minutes. Serve warm, preferably with some crusty bread and cheese on the side.