Melt butter in a large pan and add thinly sliced potatoes and onions. Toss well in the butter. Put a lid on the pan and allow the vegetables to simmer over a low heat for about 10 minutes. Don't let the vegetables turn brown. Add the milk and all other ingredients, except for the chives, and simmer for about 30 minutes. Remove thyme, bay leaf, and parsley. Pour soup into food processor or blender (on chop) for about 1 minute. Pour into soup bowls and garnish with chives. Makes 6 servings.