Bring a pot of lightly salted water to the boil and cook the fregola as you would pasta so that it is still “al dente”.
Meanwhile, lightly fry the garlic in the olive oil so it becomes golden but not dark or burnt. Add the vongole and mussels and a ladle of the fregola cooking water to the pan with the garlic. Add the saffron, turn up the heat and cook until the bivalves have opened. Remove the vongole and mussels into a bowl and strain the cooking liquid through a double layer of muslin or a clean tea towel to remove any grit. Return the strained liquid to a clean pan. Remove the top shell of the vongole and mussels exposing the meat and keep aside. Drain the fregola (keep a litre of the cooking water) and add it to the pan with the passata. Add half the parsley and another ladle of the fregola cooking water. Add a good pinch of salt and mix. Add the rest of the seafood and simmer for 5-6 minutes, adding the already cooked vongole and mussels about a minute before it finishes cooking. Add a final season with salt and pepper to taste and serve with remaining parsley.
Serves 4 as a second course