Sort and wash beans; place in a Dutch oven. Cover with water 2 inches above beans; let stand 8 hours or overnight. Drain.
Combine beans, broth, and salt in Dutch oven; bring to a boil over medium heat. Cover, reduce heat, and simmer 1 hour or until beans are tender.
Drain beans, reserving 3 cups liquid. Mash beans with the back of a spoon, and return to Dutch oven. Stir in reserved liquid.
Sauté onion and garlic in hot oil in a skillet until tender. Stir in walnuts and next 3 ingredients.
Add walnut mixture to beans, and cook until thoroughly heated. Sprinkle with cilantro and parsley.