Seafood-and-Seaweed Chowder

Name: Seafood-and-Seaweed Chowder
Cook time: 2 h 15 min
Total time: 2 h 15 min
Cuisine: American
Ingredients: 3 tablespoons canola oil; 1 large yellow onion, finely chopped; 2 medium carrots, finely chopped; 2 medium celery stalks, finely chopped; 1 1/2 cups (12 ounces) dry hard cider; 7 cups water; 1 1/2 ounces dried kelp or kombu; 10 thyme sprigs; 5 medium garlic cloves; 3 fresh bay leaves; 1 1/2 pounds mussels, scrubbed and debearded; 1 1/2 pounds littleneck clams, scrubbed; 3 tablespoons unsalted butter; 1 medium-size yellow onion, finely chopped into small cubes; 4 medium russet potatoes, peeled and cut into 3/4-inch pieces; 3 medium leeks, finely chopped into small cubes; 2 teaspoons fine sea salt, plus more to taste; 1 1/2 cups heavy cream; 1 pound skinless pollock or cod fillets, cut into 1 1/2-inch pieces; 2 tablespoons chopped fresh dill, plus more for garnish; Finely ground nori