In a medium pot, boil potatoes until crisp and tender, not quite done, drain and set aside. In a large stock pot, cook bacon until crisp. remove bacon and drain on paper towels. Leave 4 tbsps of bacon drippings in pot. Add butter and let melt. Add onion, celery, and garlic, cook until limp. Stir in flour to make a thick roux. Add clam broth, 2 cups at a time, stirring until thick and creamy. Add thyme, black pepper, and bay leaves. Cook for 15 mins until hot and bubbly. Turn heat to low. Add clams, potatoes, and bacon. Simmer for 15 mins. Add heavy cream and parsley, turn off burner and serve.