Start to finish: 1 hour
2 tablespoons unsalted butter
2 onions, cut into 1/2-inch dice
4 ounces salt pork, rind removed, rinsed, and cut into 2 pieces
1 1/2 teaspoons minced fresh thyme
Salt and pepper
1 bay leaf
5 cups water
2 pounds skinless cod fillets, sliced crosswise into 6 equal pieces
1 1/2 pounds Yukon Gold potatoes, peeled and cut into 1/2-inch dice
2 cups whole milk
1 tablespoon cornstarch
Melt butter in Dutch oven over medium heat. Add onions, salt pork, thyme, 3/4 teaspoon salt, and bay leaf; cook, stirring occasionally, until onions are softened but not browned, 3 to 5 minutes. Add water and bring to simmer. Remove pot from heat, gently place cod fillets in water, cover, and let fish stand until opaque and nearly cooked through, about 5 minutes. Using metal spatula, transfer cod to bowl.
Return pot to medium-high heat, add potatoes, and bring to simmer. Cook until potatoes are tender and beginning to break apart, about 20 minutes.
Meanwhile, whisk milk, cornstarch and 1/2 teaspoon pepper together in bowl. Stir milk mixture into chowder and return to simmer. Return fish and any accumulated juices to pot. Remove pot from heat, cover, and let stand for 5 minutes. Discard salt pork and bay leaf. Stir gently with wooden spoon to break fish into large pieces. Season with salt and pepper to taste. Serve immediately.
Nutrition information per serving: 451 calories; 204 calories from fat; 23 g fat (10 g saturated; 0 g trans fats); 91 mg cholesterol; 718 mg sodium; 31 g carbohydrate; 3 g fiber; 6 g sugar; 29 g protein.