 creme fraiche separated when cooked
I have been making a potatoes au gratin recipe that calls for a mix of 1.5c creme fraiche + 1/3c whipping cream. The first half dozen times I made it, it was fine, the last two it came out very greasy, any ideas why?
Calls for yukon gold potatoes, prefer them, used them most of the time, but used russets in one of the greasy recipes & a couple of the good ones, starts it at 400 deg for the the first 1/2 hour, then decreases to 350 for the last half hour.
Help, the recipe tastes wonderful, & I don't want to give it up because of the grease. It has been the same brand of creme fraiche, not out dated every time. (tried to make it once ages ago, was a dismal failure, has not been attempted since & have never used homemade in any of my cooking-was afraid I'd kill someone, plus it never thickened up....) | 
