what is crème fraîche and where do i get it

I would try making my own crème fraîche if I were you. It's easy (and if you live in a rural area, it'll be a lot less expensive than tracking down the real stuff). Just take heavy cream, add buttermilk (2 tablespoons buttermilk to 1 cup cream), and let it sit at room temp, covered, until it starts to smell a bit sour and thickens up. This can take up to a couple days depending on the temp.

Creme fraiche is like sour cream, only less sour. You can find it at most grocery stores, usually in the gourmet cheese section. For this dish, you definitely substitute with sour cream in a pinch.