Rinse the dried great northern beans under cold water and pick out any debris. Place the beans in a large pot and add enough water to cover them by about 2 inches. Let them soak overnight, or use the quick soak method by bringing them to a boil, removing from heat, and letting them sit for 1 hour. Drain and set aside.
In the same pot, heat a drizzle of oil over medium heat. Add the onion, carrots, celery, and garlic. Sauté until the vegetables are tender, about 5 minutes.
Add the soaked beans, ham bone, diced ham, chicken or vegetable broth, bay leaves, and dried thyme to the pot. Stir well to combine.
Bring the soup to a boil, then reduce the heat to low. Cover the pot and simmer for about 1.5 - 2 hours, or until the beans are tender and the flavors have melded together.
Remove the ham bone from the pot and discard. Using a fork, remove any remaining meat from the bone and return it to the soup. Discard the bone.
Taste the soup and season with salt and pepper as needed.
Serve the hot ham and bean soup in bowls, garnished with freshly chopped parsley. Enjoy!