Cover the dried beans in water and boil on the stove for five minutes. (Alternately, soak them overnight in water.) Drain the beans.
Transfer the beans to the slow cooker and add the remaining ingredients except the garnish ingredients.
Cook on low for 6-8 hours, or until beans are very soft. Puree the soup a bit with an immersion blender.
Garnish with any of the suggested toppings.