Sweat the vegetables: Melt the butter in a large stockpot or Dutch oven over a medium-low heat. Add the diced onion and celery. Cook for 8-10 minutes, stirring occasionally, until the onions become soft, translucent, and smell sweetly fragrant. The celery should have softened but still hold its shape. You are aiming for them to be tender, not browned.

Bloom the garlic and flour: Stir in the minced garlic and cook for 30 seconds until it releases its pungent, heady aroma. Sprinkle the flour over the vegetables and stir constantly for a full 2 minutes. The mixture will become a thick, pale golden paste (a roux) that smells nutty and cooked.

Build the broth: Slowly pour in the chicken stock and clam juice, whisking continuously to prevent lumps. The liquid will be cloudy at first, then smooth out as you whisk. Add the cubed potatoes, bay leaf, and thyme. Increase the heat to medium and bring the liquid to a gentle simmer. You should see small, lazy bubbles breaking the surface, not a rolling boil.

Simmer the potatoes: Reduce the heat to low, partially cover the pot, and let it simmer for 15-20 minutes. The potatoes are ready when you can easily pierce them with a fork, but they are not falling apart. The broth will have thickened slightly and taken on a milky appearance from the potatoes releasing their starch.

Add the clams and cream: Remove the bay leaf. Stir in the chopped clams (with their liquor) and the double cream. Gently bring the chowder back to a low simmer. Do not let it boil vigorously, or the cream may split. Cook for just 3-5 minutes, until the clams are heated through and their edges are slightly firm. The chowder will look luscious, pale cream in colour, and smell intensely of the sea and sweet cream.

Season and finish: Taste the chowder carefully before seasoning, as the clams and clam juice can be salty. Add white pepper for a gentle warmth without black specks. Stir in a little fresh lemon juice if the chowder needs a touch of brightness. The final texture should be a rich, creamy broth that coats the back of a spoon.

Rest and serve: Remove the pot from the heat. Let the chowder sit, covered, for 10 minutes. This allows the flavours to meld beautifully and the starch to finish thickening the broth. The surface will look still and creamy. Ladle into warm bowls and garnish generously with fresh chives or parsley.