Vichyssoise (chilled leek and potato soup) can also be served warm, hot.

4 Tbs butter
4 leeks, cleaned,thinly sliced, white partss only
1/2 onion chopped
2 potatoes cubed
2 cups chicken stock or broth
2 cups heavy cream, can use mix of milk, add sour crean or buttermilk.
salt and pepper
Chives

Melt butter, add leeks, sweat for 5 minutes, addd potatoes, and cook for a minute or two, add broth, cook low heat 35 minutes. then blend in blender, add cream. To make thin, add more broth.
salt, pepper to taste. Can top with chives.