2 tablespoons extra-virgin olive oil
1 large onion, thinly sliced
2 leeks, white and tender green parts only, thinly sliced
2 garlic cloves, minced
1 cup pearled barley
8 cups low-sodium vegetable broth
4 cups water
1 1/2 pounds celery root, peeled and cut into 1/2-inch cubes
1 pound parsnips, peeled and cut into 1/2-inch pieces
Salt and freshly ground pepper
1 pound baby spinach

In a large pot, heat the oil. Add the onion, leeks and garlic and cook over moderate heat, stirring occasionally, until tender, about 5 minutes. Stir in the barley. Add the vegetable broth and water and bring to a boil. Add the celery root and parsnips and season with salt and pepper. Simmer over moderately low heat until the barley and root vegetables are tender, about 40 minutes.
Stir in the spinach and simmer for 5 minutes. Season the soup with salt and pepper serve and enjoy.