Cook the fregola. Bring a medium saucepan of salted water to the boil. Add the fregola and cook until al dente (about 12 minutes). Drain well and set aside.
Heat the oil and garlic in a large saucepan over medium-low heat until the garlic begins to soften but is not colored. Add the leek and fennel and cook until softened (about 7 minutes).
Add the vermouth, increase the heat to high and cook until it has evaporated, scraping up any bits on the base of the pan (about 4 minutes).
Add the tomato, reduce the heat to medium and cook, stirring occasionally so the base doesn’t catch, until they’ve collapsed and have released their juices (about 5 minutes).
Add the stock, chilli flakes and saffron and bring to a gentle boil. Check the seasoning. Add some freshly ground pepper and a little salt, if desired, keeping in mind that the briny juices from the mussels and clams will make the dish salty too.
Add the mussels then the clams on top (as they will cook quicker), cover with a lid and cook until they have opened (about 5 minutes).
Remove from the heat, stir through the fregola, lemon juice and rind, and parsley.
Serve immediately on a large shared platter with a drizzle of extra virgin olive oil to finish.
• Fregola Sarda is rolled semolina pasta from Sardinia,