Warm the oil in a pan. Add the chopped leek, cover and gently cook for a few minutes until soft. Add the stock, bay leaf, potato and haddock. Season lightly with black pepper. Bring to the boil and simmer for 15 minutes.
Remove the haddock from the pan with a slotted spoon. When the fish is cool enough to handle, remove any skin and bones, then flake the haddock back into the pan.
Blend a ladle full of the soup in a liquidiser and return to the pan. Stir in the double cream and simmer for another 2-3 minutes. Add more black pepper if necessary, then sprinkle with the chopped chives and serve.
Serve with chunks of fresh wholemeal or granary bread.