Melt the butter in a large saucepan over a low heat. Add the leeks and potatoes and cook for 10 minutes, until softened but not coloured.
Add the stock and wine and bring to the boil. Simmer for 35 minutes until the potato is very tender. Add the crème fraîche and a quarter of the smoked salmon. Remove from heat and use a hand-held blender to purée until it has reached a smooth texture.
Return the soup to the hob on a low heat to gently warm it. Season to taste.
Just before serving, stir in the remaining smoked salmon, reserving a few strips as garnish. Divide between warmed bowls and finish with the strips of smoked salmon, a spoonful of crème fraîche and a scattering of chives.
This recipe is perfect for making in large batches and freezing to use at a later date.
In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date.
Always defrost and heat thoroughly before eating. Never re-freeze food that has already been frozen; this includes raw and cooked ingredients such as meat, fish and poultry.