01 - Cook diced bacon in a large pot over medium heat until crisp. Remove bacon with a slotted spoon and reserve. Keep 2 tablespoons of bacon fat in the pot, discarding the rest.
02 - Add butter to the pot. Once melted, sauté onions and celery for 5 to 7 minutes until softened. Add garlic and cook for an additional minute.
03 - Sprinkle flour over the vegetables and stir constantly for 2 minutes to form a roux, ensuring there are no lumps.
04 - Gradually whisk in the reserved clam juice, bottled clam juice, milk, and heavy cream until the mixture is smooth.
05 - Add diced potatoes, bay leaf, dried thyme, salt, and black pepper. Bring to a gentle simmer and cook for 15 to 18 minutes, stirring occasionally, until potatoes are tender.
06 - Stir in chopped clams with their remaining juice, cooked bacon, and fresh parsley. Simmer for 5 more minutes, then remove the bay leaf.
07 - Taste and adjust salt and pepper as needed.
08 - Ladle hot chowder into hollowed sourdough bread bowls, garnish with extra parsley, and serve immediately.