In a large soup pot, melt 2 tablespoons of butter and add 1 large chopped onion and two 2-ounce chunks of salt pork with the rind removed. Cook the onions and pork over medium heat for about five minutes, until the onion begins to soften.
Add 2 cups of bottled clam juice, 1 1/2 cups of water, 3 cups of diced russet or Yukon gold potatoes and 1 bay leaf. Season the mixture with 1 teaspoon of salt and 1/4 teaspoon of pepper, adjusting the seasonings to taste.
Bring the mixture to a boil and then reduce the heat to medium-low. Cook the broth covered for 15 to 20 minutes or until the potatoes are tender. Add 2 cups of half-and-half and 2 tablespoons of chopped fresh thyme or 2 teaspoons of dried thyme.
Add 1/2 pound of shelled Maine shrimp, 1/2 pound of sea scallops cut in half and 1 pound of haddock or other mild white fish cut in 2- to 3-inch chunks. Bring the chowder to a simmer over medium heat for about five minutes until the seafood becomes opaque. Remove the salt pork.
Cool and refrigerate the chowder, uncovered, for several hours or overnight.
Just before serving, gently reheat the chowder, adding more liquid if necessary. Season the chowder to taste and ladle it into bowls.
This recipe makes about two quarts of chowder.