Bring 3 cups water to the boil in a large frying pan over moderate heat. Add the onion, carrot and peppercorns and reduce to a simmer. Slip in the fish, skin-side-up; cover and simmer for 8 minutes or until the salmon is just cooked through. Cool in the poaching liquid. Reserving 2 tablespoons of the poaching liquid, lift the fish out, transfer to a platter, cover and put aside. Discard the remaining poaching liquid and the solids.
Whisk together the reserved poaching liquid, the mayonnaise, sour cream and lime juice in a medium bowl. When well combined, stir in the basil and chives.
Remove the salmon skin and cut the fillet into 4 portions. Serve the salmon with the sauce spooned on top.
Did you know?
One American study has shown that omega-3s suppressed the growth of breast tumours in laboratory animals.