Another quick note on the creme fraiche. Though it tastes a lot like sour cream, it behaves a lot like ultra thick whipping cream. I have never used sour cream to make a white sauce before, so I don't know if it would work the same way. A lot of american sour cream is more gelatinous (and most of it has a lot of additives). My recommendation, if you can't find creme fraiche for the previous recipe, try using regular creme. Or if you want that sour note, use an organic sour creme with no additives (or regular, non organic Daisy Brand sour creme, which lists these ingredients from what I recall: grade A creme, culture). It also comes with "inspirational" sayings on the lid, like "When there's a song in your heart, sing along!" Yay for Daisy!