01 - In a large soup pot or Dutch oven over medium heat, cook chopped bacon until crisp. Remove bacon with a slotted spoon and set aside.
02 - Using the rendered bacon fat, sauté onion, celery, and garlic for 3 to 4 minutes, stirring occasionally, until vegetables are softened.
03 - Add unsalted butter and allow it to melt fully. Sprinkle in flour and cook, stirring constantly, for 1 to 2 minutes to form a pale roux.
04 - Gradually pour in clam juice, whisking continuously to prevent lumps. Stir in diced potatoes, bay leaf, dried thyme, salt, and freshly ground black pepper.
05 - Increase heat to bring mixture to a gentle boil. Reduce to a simmer and cook for 10 to 12 minutes until potatoes are just tender.
06 - Stir in whole milk, heavy cream, and chopped clams. Simmer gently for 5 to 7 minutes, taking care not to boil after dairy is added.
07 - Remove the bay leaf. Adjust seasoning to taste. Ladle hot chowder into bowls and garnish with reserved bacon and chopped parsley. Serve immediately.