I finally got around to trying this -- it was delicious and ridiculously easy. I used creme fraiche, but then decided I needed more "sauce" and supplemented it with heavy cream. That worked fine, but I'd do all or mainly creme fraiche next time.

For anyone else who wants to try it, I preheated the oven to 400 (Farenheit) which worked well. It'll take 10 - 20 minutes depending on the thickness of the fillets.

Thanks for your advice Karen!