Slice the salt pork thin and cook in a soup pot over medium heat to render some fat. Cook the sliced onion in the pork fat until it is wilted and translucent. Add the sliced potatoes and cook for two minutes, stirring.
Add the seafood stock and thyme and bring to a boil. Reduce heat and simmer for 15 minutes.
Cut the fish into bite-size morsels and add to the chowder pot, simmer for 5 minutes. Add the heavy cream and butter and simmer 5 more minutes.
Remove and discard the slices of salt pork. Check that the fish and potatoes are done, taste, and add sea salt and black pepper as needed. Serve with oyster crackers.