1. Preheat broiler with rack 8 inches from heat source. Heat oil in a large ovenproof braiser or saute pan over medium-high heat. Add garlic, onion, and fennel; saute, stirring occasionally, until just starting to brown, about 3 minutes. Add tomato paste; season with salt and pepper and cook, stirring, 2 minutes. Stir in vermouth and saffron and cook 1 minute more.

2. Add orzo, clam juice, and broth; bring to a simmer. Stir in mussels and simmer, stirring frequently, until almost all liquid is absorbed and orzo is al dente, about 9 minutes.

3. Season shrimp and squid with salt and add to braiser with cockles, scattering throughout and nestling into orzo mixture. Broil 5 minutes. Season fish with salt and tuck into mixture. Broil until seafood is cooked through, about 5 minutes more. Let stand 5 minutes, top with parsley, and serve.