Seafood Chowder with Bacon and Thyme

Name: Seafood Chowder with Bacon and Thyme
Ingredients: 1 1/2 pounds Yukon Gold potatoes, peeled and cut into 1/2-inch cubes (about 2 large potatoes); 1 tablespoon unsalted butter; 4 ounces high-quality bacon, sliced into 1/2-inch pieces (about 4 slices); 2 celery stalks, thinly sliced on a bias (about 1/2 cup); 2 medium leeks, white and light-green parts only, halved and thinly sliced (about 1 1/2 cups); 1 garlic clove, minced; 1/2 teaspoon kosher salt, plus more for seasoning; 1/2 teaspoon fresh thyme leaves; 2 pounds skinless haddock (or cod) fillets, cut into 2-inch cubes; 3 pounds mixed littleneck clams and cockles, rinsed and scrubbed; 2 cups heavy cream; Ground white pepper; 1/4 cup freshly chopped flat-leaf parsley; Crusty bread, for serving