The clams are here for their liquor, not their meat. Everything in the method below exists to get that broth out of the shells and into the pot without diluting or grittying it. Get that right and the rest is technique.
This is the best clam chowder I have ever had
Dissolve the 66 g of salt in 8 cups of cold water — this is artificial seawater, and plain water will kill them over a long soak. Wide shallow container so they have oxygen, not a packed bucket. Into the fridge.
Stiff brush under cold running water, no soap. Work the concentric growth ridges and the hinge, where mud packs in. Whatever's on the outside of the shell washes into your broth.
Discard any that are cracked, or that gape and won't close when tapped.
Bring the wine and water to a boil in a wide, deep pot with a tight lid. Add as many clams as fit — two deep is fine, steam does the work — cover, and pull each one with tongs the moment it gapes half an inch.
Then put the next batch into that same liquid. Do not start fresh wine and water. The liquor concentrates with every round instead of getting split three ways. Add a splash of water only if it threatens to cook dry.
Clams this size run long. Start checking at 10 minutes and give a stubborn one up to 20 before you call it dead.
Let the pot liquor stand undisturbed so the sand drops out. Line a sieve with four to six layers of cheesecloth, wet it and wring it out — dry cloth drinks your broth and leaves a papery note.
Ladle off the top rather than tipping the pot, and stop about half an inch from the bottom. Don't squeeze the cloth or scrape the pot; both force trapped grit through. Sacrifice that last bit.
Snip off the dark siphon tip, cut out the adductor muscles if they didn't stay on the shell, and trim anything on the foot that feels rubbery between your fingers. The soft belly is good eating, though it's the most assertive part and you can leave it out.
Chop to ¼ inch, cutting the foot across its width so the fibers come out short. Work over a bowl — the liquid that runs out goes into the broth. Refrigerate the meat; it does not go in today.
Medium-low in a heavy Dutch oven until the fat runs clear and the bits are golden. Lift the cracklings out and save them for the table. Pour off all but 3 tbsp of the fat and jar the rest.
Onions and the herb bundle into that fat, medium-low, until fully soft with no color at all. Browning here makes the chowder taste like onion soup.
Stir it in and cook until it smells nutty but stays pale.
Measure the strained liquor. Top it up with bottled clam juice first, since that's clam flavor, and use unsalted chicken stock only for whatever's left after that. Whisk it into the pot a cup at a time so no lumps form.
In they go, lid on, at a bare simmer until fully tender. Two pounds of potato in four cups of liquid will sit proud at the start, so stir every few minutes or the top layer cooks unevenly.
Cooking them in the clam broth instead of water is what makes them taste like chowder rather than potatoes sitting in chowder.
Press it against the side of the pot with a wooden spoon and stir it back in. Do not reach for an immersion blender — high-speed blades rupture the starch cells and turn the whole pot gluey in about two seconds, with no way back.
Cream, milk, butter and pepper. Low heat until steaming and no further. A boil breaks the cream and the texture goes grainy.
No salt yet. The clam liquor carries most of it and you have no idea where you'll land until tomorrow.
Pull the herb bundle. Ice bath in the sink or split into shallow containers — a hot covered pot in the fridge stays warm for hours. Cover once barely warm.
This rest is the single highest-leverage step in the recipe. The starch sets into something properly creamy, and the pork and clam flavor migrate into the potatoes, which today still taste mostly like potato.
Low and slow, stirring often, never above a lazy simmer. When it's steaming, kill the heat and stir in the chopped quahog meat. Three or four minutes of residual heat cooks it through; anything more turns it to rubber.
Now judge the volume. Aim for roughly 450 g of clam meat in the pot all told. If your quahogs came up short, drain the canned clams and add them here alongside the fresh, a can at a time, until it looks right to you. Half canned by weight is fine — the broth is doing the flavor work and nobody will read it as a canned chowder. Past about 550 g it stops being chowder and becomes a clam dish with potatoes in it.
Now taste. Between the liquor and any canned clams you may need very little salt, or none. Then the teaspoon of vinegar or sherry, off the heat — it cuts the richness and lifts everything.
If it's thicker than you want, loosen with milk, not water.
Cracklings scattered on each bowl at the table so they stay crisp. Crackers alongside. Tabasco for anyone who wants it, which is traditional and not an insult to the cook.
Transport the base cold and do steps 14 through 16 in the destination kitchen. Bring your own heavy pot if theirs is thin — three quarts of cold cream soup on an unfamiliar stove is the likeliest way to scorch it after doing everything else right.