Melt the butter in a saucepan, add the shallot and cook for 3 minutes until softened. Pour over the vermouth and bubble for 5 minutes until reduced by half. Add the stock, then place the salmon in the pan, making sure it is covered with liquid, and gently poach for 5–10 minutes or until the fish is cooked through and flakes easily. Remove from the pan, discard the skin and flake into bite-sized pieces.
Add the prawns to the pan, then add the scallops and cook for a further 2 minutes or until just cooked through. Set aside with the salmon.
Add the cream to the pan and bubble until reduced down to a sauce, then season. Carefully stir in the reserved seafood, heat through and add the chives.
Meanwhile, cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Drain, then toss through the seafood sauce and season. Serve sprinkled with extra chopped chives.