Preheat oven to 180°C (160°C fan-forced).
Heat 1 tablespoon olive oil in a large frying pan over medium heat.
Add pancetta and onion. Cook for 5 minutes until lightly browned.
Stir in garlic and capers. Cook for 1 minute until fragrant.
Add tomato paste and chilli flakes (if using). Stir for 30 seconds.
Gradually pour in chicken stock, stirring to combine.
Add cream and stir until smooth.
Transfer the sauce mixture to a 2.5L ovenproof baking dish.
Wipe the pan clean and heat remaining olive oil over medium-high heat.
Sear salmon, top-side down, for 2 minutes until golden.
Remove salmon and cut or break into large chunks.
Add salmon pieces and prawns to the baking dish, nestling into the sauce.
Bake for 20 minutes until seafood is cooked through and sauce is bubbling.
Season with salt and freshly ground black pepper.
Sprinkle with fresh basil leaves.
Serve hot with crusty bread.