leek and thyme souprating:
2 large sprigs of thyme
300ml semi-skimmed milk
salt and black pepper
600ml double cream
top and tail the leeks, and cut into thick slices (discard any coarse outer leaves). Cut the potatoes into rough dice, about 2.5cm, and dry on kitchen paper.
melt butter in large saucepan, add leeks and 1 thyme sprig. Cover and cook for 4-5 minutes until softened. Add potato pieces, and just enough cold water to cover the veg. Re-cover, and cook over low heat for 30 minutes.
pour in milk and add seasoning, cover and simmer for a further 30 minutes. You will find that some of the potato breaks up, leaving you with a semi pureé and rather lumpy soup.
remove the thyme sprig (the leaves will have fallen into the soup) and serve. Add garnish if wished.