This is a lovely soup to serve in the summertime, as it is served chilled. If you prefer, you can substitute sour cream for the creme fraiche. To make creme fraiche, just combine 1 cup of whipping cream with 2 tbsp of buttermilk. Once combined, cover and let stand at room temperature for 8 hours. This will make a cup of creme fraiche. Prep and cooking time does not include the chill time!