Halve leeks lengthwise, wash carefully, and slice thinly.
In large heavy pan, lightly sauté leeks in butter. Dry potato cubes and toss with leeks. Sauté again for about 3 minutes.
Add asparagus, stock, salt, and pepper.
Bring to a boil, lower heat, and simmer gently for 30 to 40 minutes until all vegetables are very soft. Put contents in food processor or blender and puree.
Add cream and adjust for seasoning. Garnish with chives.
