Step 1

Combine ham bone and 4 quarts of water in a large stock pot of Dutch oven at least the night before. Bring to a boil, cover, reduce heat and simmer for 10 to 12 hours.

Step 2

In the meantime, place beans in a large pot with water to cover; soak overnight. Drain beans the next day and return to the pot.

Step 3

Remove ham bone from the pot and pick off any edible meat. Strain the stock and measure out 3 quarts for the soup. Remaining stock can be frozen.

Step 4

Pour 3 quarts of stock over the soaked beans. Add ham, celery, carrots, onion, and garlic. Season with salt and pepper. Bring soup to a boil, then reduce heat to a simmer. Cover, tilting the lid to allow steam to escape, and simmer until beans are tender, 1 1/2 to 2 hours. Add sherry in the last 30 minutes of cooking and season with salt and pepper.

Step 5

Ladle soup into bowls and sprinkle with fresh parsley.