Toast fennel seeds in a large sauté pan over medium heat for 2 minutes until aromatic.
Add chorizo chunks, rosemary, garlic, chilli, and a drizzle of oil to the pan and cook for 2 minutes.
Stir in tomatoes, wine, harissa paste, and oregano, then simmer for 15 minutes until thickened.
Boil the linguine in a large pan of water according to the packet instructions.
Incorporate the prawns and mussels into the sauce for the final 5 minutes of cooking.
Drain the pasta and toss with olive oil, salt, and pepper in the warm pot.
Season the sauce with salt, pepper, and sugar if needed, ensuring the mussels have opened.
Combine the sauce and pasta, divide into plates, and garnish with fresh parsley.