Rinse the clams under cold running water to remove any surface dirt. Place them in a large bowl of cold, salted water. (To purge the sand from 36 to 42 clams, use a solution of ? cup of salt per 1 gallon of cold water. The amount of clams (36 to 42) will determine the container size, but the crucial factor is the salt-to-water ratio.) You need enough solution to fully submerge the clams with room for them to open and expel sand. Let the clams soak for 2 hours; Roy prefers soaking them for up to 6 hours, changing the water at least twice and adding salt each time. Many people soak them overnight. Some people do it all day.

Drain and rinse the clams again before cooking.

Bring a large pot of water to a boil for the pasta.

Place a wide pan over medium heat and add the clam juice, vermouth or white wine, and the clams. Cover, and turn heat to medium. Cook for 10-15 minutes. You will start to hear the clams open at different times around the 10-minute mark ; remove them from the pan with a slotted spoon as soon as they open and reserve them in a bowl. Discard any that remain closed after 15 minutes of cook time. Cook to reduce and concentrate the liquid in the pan, about 5 minutes.

While the liquid reduces, shell half of the reserved clams.

When the water is at a boil and half of the clams are shelled, drop in the pasta. Cook pasta about 3 minutes under the package directions for al dente, stirring occasionally. When done, reserve 1 cup of the pasta cooking water.

While the pasta cooks, add 2 tablespoons of butter to the clam sauce along with the chopped garlic, olive oil, and a pinch of red pepper flakes. Stir gently over medium heat until the butter melts and the ingredients are well-combined. Return shelled and unshelled clams to the pan. Turn off heat but leave the pan stove.

Use tongs, drop the pasta directly into the pan with the clams. Turn the heat back on under the clam sauce to medium and toss to coat the pasta in the sauce,gradually adding about a ½ cup of the reserved pasta water, a ¼ cup at a time. The starch in the pasta water will emulsify with the butter, olive oil, and clam juices to create a silky sauce. Toss constantly, until the sauce thickens and the pasta is al dente, about 2 minutes

Add the remaining 3–4 tablespoons of butter, ½ cup Parmesan, and parsley. Toss to coat then taste and adjust seasoning with salt, pepper, lemon juice if using, more red pepper and additional Parmesan as needed and serve immediately.