In a large heavy-bottomed pot or Dutch oven, cook the chopped bacon over medium heat until crispy, about 6-8 minutes. Remove bacon with a slotted spoon and set aside, leaving the fat in the pot.

Add butter to the bacon fat and melt over medium heat. Add diced onion and celery, cooking until softened, approximately 5-7 minutes. Stir in minced garlic and cook for another minute.

Sprinkle flour over the vegetables and stir constantly for 2-3 minutes to create a roux, ensuring the flour is completely incorporated.

Gradually pour in the clam juice while whisking constantly to prevent lumps. Bring to a gentle simmer and cook until slightly thickened, about 3-4 minutes.

Add the scrubbed clams to the pot, cover with a lid, and steam for 8-10 minutes until all clams have opened. Discard any clams that remain closed.

Remove clams from the pot and set aside to cool. Once cool, remove clam meat from shells, roughly chop, and discard shells.

Add diced potatoes, bay leaves, and fresh thyme to the pot. Simmer uncovered for 15-20 minutes until potatoes are fork-tender.

Reduce heat to low and stir in heavy cream and whole milk. Add the chopped clam meat and reserved bacon. Season with salt and pepper to taste.

Continue cooking on low heat for another 5-7 minutes, stirring occasionally. Do not allow the chowder to boil once cream is added.

Remove bay leaves and adjust seasoning. Ladle into bowls and garnish with fresh parsley and oyster crackers.