Drain beans in sink. Return to 10-12-quart pot; add 3 quarts water (You will probably need to add more as the beans cook), salt, pepper, bay leaves, onions, celery, carrot and garlic. You can add a meaty hambone here or later add 2 cups of diced ham. Cover, set over high heat, and bring to a boil. Reduce to simmer and cook an hour, stirring regularly and skimming away scum that comes to the top.
Remove hambone, cool briefly, trim off bits of ham, return them to the beans, and discard hambone. (Or add 2 cups diced ham.) Stir in the handful of minced fresh parsley, and bring to a boil. Reduce to simmer once more, and let cook, stirring regularly, until beans are tender and creamy—perhaps another hour. Add more water as needed to keep the beans in a barely brothy bath as they simmer. Taste broth and beans; season as needed. Add a few shakes of Tabasco to taste, if using.
Serve hot seasoned with a drizzle of red wine vinegar if you like. Fresh cornbread and butter is a tasty accompaniment.
Leftovers can be stored in the fridge for 3-4 days including the day the ham is baked or frozen in tightly covered containers 4-6 months.