A delicious, aromatic supper you can prepare in the morning and let cook the whole day. Come home hungry to a filling meal.
Precook beans: Place beans in a medium saucepan. Cover beans with water (enough to cover by one or two inches). Bring to a boil over medium-high heat, then lower to a simmer and cook covered for about 30 minutes (or until beans are firm, but tender enough to be pierced by a fork). Drain beans and rinse. Set aside.
Place beans, water, tomatoes with juice, garlic, celery, carrots, onion, barley, skirt steak, bay leaf, salt, herb blend, pepper, and mushrooms in a slow cooker; cover and cook on low until the beans are quite tender and the soup is thick, about eight hours.
Just before serving, stir in the spinach and vinegar, cover and let the soup cook until the spinach wilts, about five minutes. If soup is too thick, adjust consistency by adding hot water by the quarter-cupful and stir. Season to taste with salt and pepper. Drizzle each serving with olive oil.
To cook this soup on the stove top, precook beans as directed above for 45 minutes. Rinse and drain, then place all ingredients (except for spinach, balsamic vinegar, and olive oil) in a large stock pot over medium-high heat. Bring to a boil, then reduce heat and simmer for one and a half hours, stirring occasionally. Add the spinach and balsamic vinegar in the last five minutes of cooking time.