For a New Orleans-style twist on this creme fraiche filling, replace half the regular cream cheese with the Creole variety, which has a thick layer of cream on top and a slightly liquid layer on bottom; drain it before using, if desired.
In the bowl of an electric mixer fitted with the paddle attachment, beat cream cheese and vanilla until soft In a separate bowl, whisk creme fraiche with a balloon whisk until it holds soft peaks.
Whisk a third of the creme fraiche into cream-cheese mixture to lighten. Fold in remaining creme fraiche while gradually sifting the confectioners' sugar over the top; fold just until combined. Cover with plastic wrap; place in refrigerator until ready to use, up to 2 hours.