3 ½ pounds relatively small littleneck clams (about 24 to 30 clams), very well scrubbed
2 tablespoons olive oil, plus more for drizzling
2 tablespoons unsalted butter
4 ounces dried chorizo, bacon, pancetta or guanciale, chopped (optional)
4 garlic cloves, thinly sliced, plus another clove for serving
½ cup dry white wine (avoid anything overly oaky, sweet or “creamy”)
2 large stalks celery, trimmed and thinly sliced on the bias, plus leaves for serving
Kosher salt and ground black pepper
½ cup parsley, tender leaves and stems
½ cup chopped chives
1 tablespoon finely grated lemon or lime zest, plus 1 tablespoon fresh lemon or lime juice
Crusty bread or thick toast, for serving
Preferably using a natural bristle kitchen scrubber (a brand new kitchen sponge will work as well), scrub the clams well under running water. After the clams have been scrubbed and scrubbed again, let them hang out in a large bowl of cold water. This will allow any residual sediment or grit to free itself from the shells and settle at the bottom of the bowl while you do everything else.
Heat oil, butter and chorizo or other pork product, if using, in a large pot (make sure it has a lid) over medium heat. Cook, swirling the pot occasionally until the butter has started to brown a little and the fat has begun to render from the pork, 3 to 4 minutes. (The pork won’t be crispy, but that’s O.K.; you’re not looking for that.)
Add the garlic and cook, stirring a minute or two until it begins to take on a toasty, light golden-brown color. Add wine and cook, letting it simmer until it’s a little more than halfway reduced, 2 to 3 minutes. Add celery and season with salt and pepper. Cook, stirring occasionally until the celery is bright green and just tender, 2 to 3 minutes. Add clams and shake the pot so they settle nicely. Place the lid on the pot and give it the occasional shake, letting them steam open and release their juices, 3 to 5 minutes. (Larger clams will take longer.) The shaking of the pot is not only fun to do, but it gives all the clams quality time with the hottest part of the pot, which will encourage them to open around the same time, although there’s always one or two clams late to the party. If there’s one that just never makes it to the party (as in, it never opens), it’s dead and should be thrown away.
Toss the parsley, chives and celery leaves in a small bowl, then add lemon or lime zest and juice, and season with salt and pepper. Serve the clams with a hunk of crusty fresh bread or thick slices of toast that have been drizzled with lots of olive oil and rubbed with a cut clove of garlic, scattering the parsley mixture over everything.