New England Style Clam Chowder

Name: New England Style Clam Chowder
Ingredients: 1 pound new or yukon gold potatoes, peeled; 6 tablespoons unsalted butter, divided; ¼ cup all-purpose flour; 20 cherrystone clams, scrubbed; 4 ounces salt pork or unsmoked bacon, sliced into three long, 1-inch-thick strips; 3 ribs celery, chopped (about 1 cup); 1 medium spanish onion, chopped (about 2 cups); 2 garlic cloves, finely chopped; 1½ quarts heavy cream; 1/2 cup chopped flat-leaf parsley; 2 tablespoons fresh thyme leaves; Salt and freshly ground black pepper; Cayenne pepper; Oyster crackers, for serving