In large pot, place garlic, onion, celery, carrot sand seasonings. Add enough broth to cover the vegetables (start with 6 cups and add more as needed). Cover and simmer until vegetables are tender, about 30 minutes.
Add Great Northern Beans, cooked ham, tomatoes and salt to taste. Check seasoning flavor and add more thyme, black pepper or salt, if needed.
Simmer uncovered for 15 minutes; serve.
Garnish with sour cream and fresh tomatoes (optional).