Pick over beans; soak overnight in plenty of water. Drain.

Put a Dutch oven over medium-high heat and add sausage. Cook, stirring often, until sausage is browned; use a slotted spoon to remove to a bowl and set aside.

Add bacon grease; when hot, add onion and celery and cook, stirring occasionally, until vegetables are translucent. Add white parts of green onions and cook 2 minutes; add garlic and cook until fragrant, about 1 minute. Add drained beans, tomatoes, enough Ham Bone Stock to cover the beans by 2 inches, bay leaves, and salt, pepper, and cayenne to taste. Stir in about a third of the cooked sausage. Bring to a simmer and cook, stirring occasionally, until beans are very soft, 1½-3 hours, depending on the age of the beans; add additional water or stock as needed.

About 30 minutes before the beans are done, add ham and remaining sausage; taste and adjust seasoning. Stir in green onion tops just before serving.

Ham Bone Stock:

Put all ingredients in a large stock pot. Bring to a simmer and cook, adding water as necessary, for about 3 hours. Use tongs to remove the ham bone to a bowl and set aside or discard. Strain stock and discard solids. Refrigerate stock overnight, then remove fat cap from stock; save for another use or discard.