Directions

1. Put the clams in a large, heavy Dutch oven, add 4 cups water, then set over medium-high heat. Cover, and cook until clams have opened, approximately 10 to 15 minutes. Clams that fail to open should be discarded. Strain clam broth through a sieve lined with doubled-up paper towels, and set aside. Remove clams from shells, and set those aside as well.
   
2. Rinse out the pot, and return it to stove. Add butter, and turn heat to medium-low. Add bacon and cook, stirring occasionally, until the fat has rendered and the pork has started to brown, about 5 to 7 minutes. Use a slotted spoon to remove bacon, and set aside.
   
3. Add onions, garlic, celery, green peppers and carrots to the fat, and cook, stirring frequently, until the vegetables are soft but not brown, about 10 to 15 minutes. Stir in potatoes, and continue cooking until they have just started to soften, about 5 to 7 minutes. Add clam broth, thyme, and bay.
   
4. Partly cover the pot, and simmer gently until potatoes are tender, about 10 to 15 minutes. Using the back of a wooden spoon, smash a few potatoes against the side of the pot to release their starch and help thicken the broth.
   
5. Meanwhile, chop the clams into bits. When potatoes are tender, stir in tomatoes, and heat them through. Add chopped clams and bacon, stirring to combine. Add black pepper to taste. Let chowder come to a simmer, and remove from heat. Fish out the thyme and the bay leaf, and discard. Season with salt, as needed.
   
6. The chowder should be allowed to sit for at least an hour to cure. Reheat it before serving, then garnish with chopped parsley.