If you have a whole salmon or sea trout, or you've bought a fillet, there are always leftover trimmings – and adding a few flakes to a chilled vichyssoise is a great way to use them up. You can also add chunks of cooked leek and potato to the soup if you wish.
2 medium leeks, roughly chopped
1tbsp olive oil
250g good-quality potatoes, such as desirée or maris pipers, peeled and roughly chopped
1 litre vegetable stock (or a good quality cube)
A couple of spring onions, roughly chopped
1tbsp chopped chives
120-150g lightly poached salmon
2tbsp crème fraîche or sour cream
In a covered pan gently cook the leeks in the olive oil without colouring for 4-5 minutes. Add the potatoes and vegetable stock, bring to the boil, lightly season with salt and pepper and simmer for 10-15 minutes or until the potatoes are just cooked. Add the spring onions and simmer for another 2 minutes.
Blend until smooth in a liquidiser, then strain through a fine meshed sieve. Check the seasoning and add a little more salt and pepper if necessary. Cool the soup down in a bowl over some iced or cold water, stirring occasionally. When the soup is cold it will thicken so you may need to adjust with a little more stock, or milk as you prefer.
To serve, pour the soup into large, chilled soup bowls or soup plates then arrange the salmon in the centre with a half-spoonful of crème fraîche on top and scatter the chopped chives.