Heat butter over medium heat. Fry the scallops for 2 minutes then flip and cook for another 30 seconds. Set aside.
In the same pan, sauté until the onion is translucent. Add the minced garlic and chilli flakes and cook for 30 seconds.
Add the remainder of the marinara ingredients, stir and simmer for 15-20 minutes.
While the sauce is simmering, cook the pasta as per packet instructions, drain and reserve once cooked.
5 minutes before serving, add the prawns to the sauce, then place the mussels over the sauce and cook for 5 minutes.
Once the seafood is cooked, add the drained pasta and reserved scallops to the sauce and toss until well coated.
Serve and garnish with finely grated parmesan and parsley.