1. Place bacon fat (or a chunk of salt pork) in a Dutch Oven or large saucepan over medium heat. Add bacon, onion, and celery. Saute 10 minutes. Add potatoes, clams, clam juice, and enough water to cover. Bring to a boil, lower heat, and add half-and-half. (Do not boil or soup will curdle.) Cook on low until potatoes are soft, about 20 minutes. Season with salt, pepper, and cayenne. Cool and refrigerate overnight, reheat, and serve a day later with oyster crackers.