Plan ahead if you are making the homemade creme fraiche. It takes 24-36 hours to culture. However, you should make this, it will make you happy. There's 2 variations for culturing the cream, buttermilk or sour cream. The culture ultimately dictates the flavor of the creme fraiche; sour cream will give a slightly sweeter and creamier texture, buttercream will give you a bit more tang. Glaze and creme fraiche can be made ahead of time. Re-whisk both before using. Enjoy!