1. Rinse clams under cold water and scrub to remove grit.

2. In a large pot, add 1 cup water or clam juice and bring to a simmer, then add clams, cover, and steam until they open, about 6–8 minutes; discard any closed clams, chop meat, and reserve cooking liquid.

3. Cook bacon in a clean large pot or Dutch oven over medium heat until crispy, then remove bacon and reserve fat.

4. Add butter to the bacon fat, then sauté onion, celery, and garlic until softened, about 5 minutes.

5. Sprinkle flour over the vegetables and stir constantly for 1–2 minutes to form a roux.

6. Gradually whisk in reserved clam liquid and bottled clam juice until smooth and slightly thickened.

7. Add thyme, bay leaf, and diced potatoes, then simmer gently for 10–12 minutes until potatoes are tender.

8. Lower heat and stir in heavy cream and milk, keeping the heat low to prevent boiling.

9. Fold in chopped clams and reserved bacon, season with salt and pepper, and heat through for 5 minutes.

10. Remove the bay leaf, ladle chowder into bowls, and garnish with parsley.