Fill a large mixing bowl with cold water and whisk in the polenta until the water clouds, then add the clams and soak for 30 minutes. This is the whole trick, and it is worth knowing why it works: a clam is a filter that only runs when it is being fed. Plain water gives it no reason to open. A little grain does, and as it pumps and feeds it pushes the sand out along with everything else. Cornmeal does the same job if that is what is in the pantry.

Lift the clams out of the water rather than pouring the bowl out, or you tip every grain of sand you just worked for straight back over them. Discard the cloudy water, refill with fresh cold water, return the clams, and soak for another 30 minutes.

Repeat this soaking and draining process for 2 – 3 cycles until there is no visible sand at the bottom of the bowl. Discard any clams that stay open and do not close when tapped firmly.

Rinse the purged clams under cold running water, drain well, and set aside.

Heat a small skillet over medium heat and add olive oil.

Add panko and a pinch of kosher salt, then cook, stirring frequently, until the breadcrumbs are evenly golden and crisp, about 3 – 4 minutes.

Stir in red pepper flakes and lemon zest, toast for 10 – 15 seconds just to bloom the aromatics, then transfer the breadcrumbs to a plate to cool and stay crisp.

In a large skillet, combine olive oil, sliced garlic, and red pepper flakes. Set over medium heat and cook, stirring occasionally, until the garlic is lightly golden at the edges and fragrant, about 3 – 5 minutes, adjusting the heat as needed to keep it gently sizzling without burning.

Add white wine and bring to a simmer, then add the clams and immediately cover the skillet. Increase the heat to high and cook, checking every 30 seconds and transferring clams to a large bowl with tongs or a slotted spoon as they open, until all clams have opened, about 4 – 5 minutes in total.

Remove the skillet from the heat and let the clams cool just enough to handle, then remove the meat from most of the shells, keeping a few clams shell-on for garnish. If any clam meat is very large, roughly chop it into bite-size pieces. Strain the clam cooking liquid through a fine mesh strainer back into the skillet to remove any sand or grit.

Bring a large pot of water to a rolling boil and season with kosher salt for about 1 % salinity (for roughly 12 cups of water, use 3 tablespoon salt).

Add bucatini and cook until just shy of al dente, about 1 minute less than the package instructions, then reserve at least 1 cup of the starchy pasta water.

Using tongs, transfer the bucatini directly from the pot into the skillet with the strained clam liquid, along with a few tablespoons of pasta water. Set the skillet over high heat and cook, tossing and stirring quickly, until the liquid reduces and begins to form a light, glossy coating on the noodles. Taste the sauce here. If you feel astringency at the back of your throat, the wine has not cooked off yet, so keep it moving over the heat a little longer before the butter goes in.

Add butter and all of the clam meat, including the reserved shell-on clams, then toss gently until the butter melts and the clams are heated through, about 1 minute.

If the sauce looks tight or greasy, add more pasta water 1 – 2 tablespoons at a time, tossing between additions, until it looks silky and lightly creamy from the emulsified starch.

Taste and adjust seasoning with additional salt if needed, then remove from the heat and stir in parsley and a drizzle of fresh olive oil.

Twirl portions of bucatini into warm shallow bowls, forming tall nests of pasta.

Arrange the shell-on clams on top of each portion and spoon any remaining sauce from the skillet over the pasta.

Finish each bowl with a generous shower of chili breadcrumbs and an extra drizzle of olive oil if desired, then serve immediately.