Potato Leek Soup--Vichyssoise

It has been so warm throughout the country, that a cold soup sounds like the perfect way to start a meal. This soup can be served either cold or warm. It is a such a delicate soup that I think it benefits from the addition of just a little garlic.
The cream is optional, creme fraiche or sour cream can also be used as a garnish on top.

1 Tablespoon butter

Cold Potato Leek Soup--Vichyssoise

1 Tablespoon olive oil
3 large leeks, halved lengthwise, cleaned, and sliced into 1 inch slices, white and light green parts only
1 teaspoon salt
1/4 teaspoon dried thyme
4 cups Yukon Gold potatoes, peeled and diced into 1 inch cubes
4 cups chicken or vegetable stock
1 garlic clove, minced
salt and preferably white pepper, to taste
1/2-1 cup cream (optional)
fresh sliced chives for garnish

Melt butter in a large saucepan with olive oil over medium low heat.
Add leeks, salt and cook until softened (not browned).
Add thyme, potatoes, stock and garlic to saucepan and cook until potatoes are tender, about 15 minutes.
Add cream if desired, and simmer 10 minutes,
Season with salt and pepper.
Serve or chill and garnish with fresh chives.