If using live littleneck clams, scrub shells under cold running water. Place clams in a pot with about 100 ml water, cover, and steam over medium-high heat until shells open (4–6 minutes). Remove clams with tongs as they open and reserve the steaming liquid. Let clams cool, then remove meat from shells and chop roughly. If using canned/chopped clams, drain, reserving the liquid and add bottled clam juice to make up the indicated amount.

Render bacon and sweat aromatics

In a large heavy-bottomed pot over medium heat, add diced bacon and cook until the fat renders and edges are crisp (6–8 minutes). Transfer most of the cooked bacon to a small bowl, leaving about 1–2 tablespoons of bacon fat in the pot. Add 2 tbs butter to the fat. When butter melts, add the diced onion and celery and a pinch of salt. Cook, stirring occasionally, until onion is translucent and vegetables are softened, about 6–8 minutes. Add the minced garlic and cook 30–45 seconds until fragrant.

Make the roux and add liquids

Sprinkle the flour over the softened aromatics and stir continuously for 1–2 minutes to cook the raw flour taste, forming a light blond roux. Gradually whisk in the reserved clam juice (or bottled clam juice) and the chicken/vegetable stock to avoid lumps. Add the diced potatoes, bay leaf, and dried thyme. Increase heat to bring the mixture to a gentle simmer.

Simmer until potatoes are tender

Reduce heat to medium-low, cover partially, and simmer until potatoes are fork-tender, about 12–15 minutes. Stir occasionally to prevent sticking. Taste the broth and adjust seasoning lightly with salt and pepper, remembering the bacon and clams add saltiness.

Finish with clams, milk, and cream

Once the potatoes are tender, stir in the milk and heavy cream and warm gently—do not boil vigorously to avoid curdling. Add the chopped clam meat and two-thirds of the reserved cooked bacon. Heat just until clams are warmed through, about 2–3 minutes. Remove bay leaf. If the chowder is too thin, simmer uncovered for a few more minutes to thicken; if too thick, add a splash more milk or stock.

Season and serve

Stir in freshly ground black pepper and adjust salt to taste. Ladle chowder into warmed bowls and garnish with remaining crispy bacon, chopped parsley, and optional chives.

Optional: Oyster Croutons / Topping

While the chowder simmers, heat 1 tablespoon butter in a small skillet over medium heat. Add bread cubes and toss until golden and crisp, 5–7 minutes. If using oysters, add them in the last 1–2 minutes just to warm (do not overcook). Scatter the toasted bread and oysters over each bowl as a rustic topping.