Vichyssoise

Melt the butter in a large saucepan over low heat. Add the finely chopped leek and celery and cover the saucepan with greased wax paper. cook for 15 minutes, stirring occasionally, or until soft. Add the potatoes, diced, and the broth. season with salt and freshly ground black pepper.
bring the soup to a boil, lower the heat and cook for about 15 minutes, or until the potatoes are soft. puree the soup, pour into a bowl and add the heavy cream, salt and pepper. Cover with a plastic wrap and wait for it to cool before storing in the fridge, at least 2 hours.
Serve in chilled bowls, lightly whipped cream and sprinkled with chives.