1 For the soup: Heat the butter in a saucepan and sweat the leek until tender. Add the peas and vegetable stock and simmer for 15 minutes.
2 Puree until smooth (keeping back a few peas if desired), pass through a sieve, and pour back into the pan. Stir in the cream (return the whole peas to the pan), season with sugar, salt, and pepper and reheat.
3 For the croutons: Cut the crusts off the bread, cut into cubes and fry in butter on all sides. To serve, ladle into bowls, sprinkle with croutons and place a few blobs of crème fraiche in each bowl. Serve garnished with mint.