Cook Bacon:
In a large pot or Dutch oven, cook the diced bacon over medium heat until crisp. Remove with a slotted spoon and set aside, leaving the drippings in the pot.
Sauté Vegetables:
Add butter to the bacon drippings. Stir in the onion, garlic, and celery. Cook until softened, about 4–5 minutes.
Add Flour:
Sprinkle the flour over the vegetables and stir to form a roux. Cook for 1–2 minutes to remove the raw flour taste.
Deglaze and Simmer:
Gradually stir in clam juice (from the bottle and reserved from canned clams) and 1 cup water. Add potatoes, bay leaf, and thyme if using. Bring to a boil, then reduce to a simmer. Cook until potatoes are fork-tender, about 12–15 minutes.
Finish with Dairy & Clams:
Stir in the milk, cream, and chopped clams. Simmer gently for another 5 minutes—do not boil or the milk may curdle. Remove bay leaf.
Season & Serve:
Season with salt and pepper to taste. Ladle into bowls, top with crispy bacon and optional parsley. Serve hot with oyster crackers or crusty bread.