Peel the asparagus and cut off the bottom. Place the asparagus with the peel and the stalks in a saucepan with the vegetable stock, bring to the boil and simmer gently for 20 minutes. When the asparagus is tender, remove and chop. Strain the broth and place in a saucepan or bowl. Discard the peel and stalks.
In a large soup pan, gently sauté the leeks and asparagus in the butter. Add the flour and stir well until it thickens, adding a little broth each time until you have a nice thick soup. Puree the soup and season with salt and pepper. Fry the Parma ham until crisp. Pour the soup into a bowl, add a little double cream, top with the ham and garnish with chives. Delicious with puff pastry cheese sticks.