Rinse the scrubbed mussels under cold running water. Pull off any remaining beards with a sharp tug. Discard any mussels that are open and don't close when tapped firmly on the counter.

Set the cleaned mussels aside in a colander and let them drain while you prepare the rest.

Bring a large pot of water to a boil for the pasta. Add 1 tbsp coarse salt once boiling.

Heat 3 tbsp olive oil in a large wide skillet over medium-low heat. Add the sliced garlic and, if using, the chili flakes. Cook for 2 minutes until the garlic is pale golden and fragrant. Do not let it brown.

Add the cherry tomatoes and increase the heat to medium. Cook for 3 minutes, pressing them lightly with the back of a spoon until they begin to soften and release juice.

Raise the heat to high. Add all the mussels to the pan and pour in the white wine. Cover immediately with a tight-fitting lid and cook for 3 to 4 minutes, shaking the pan once halfway through, until all shells have opened.

Remove the lid. Discard any mussels that have not opened. If you prefer a cleaner presentation, remove half the mussels from their shells and set aside, leaving the rest in shell for plating. Keep the pan and all the broth over low heat.

Add the cavatelli to the boiling salted water. Cook for 2 minutes less than the package al dente time, then ladle out a cup of pasta cooking water before draining.

Drain the cavatelli and transfer directly to the mussel pan. Increase the heat to medium-high. Toss the pasta through the broth and cook for 2 to 3 minutes, adding a splash of pasta water if the sauce reduces too fast, until the cavatelli is al dente and has absorbed most of the broth.

Stir in half the chopped parsley. Taste the broth before adding any salt - the mussel liquor is often salty enough on its own.

Remove from the heat. Drizzle with the remaining 1 tbsp olive oil. Divide into warmed shallow bowls, making sure each portion has a few mussels in shell on top. Scatter the remaining parsley over each bowl and serve immediately.