I think this is the perfect dinner party recipe! Easy enough for a beginner cook to handle and yet really impressive! I see no reason why you can't prepare this recipe in advance, up to the wrapping in foil stage, then refrigerate it until you're ready to cook it - perhaps adding 15 minutes to the cooking time. You could substitute a half and half mixture of ordinary sour cream and double cream for the creme fraiche, but the creme fraiche is best and won't separate. This dish is rich, so it only needs simple side dishes. I serve it with Potatoes Anna Recipe #103214 and a steamed green vegetable. It also reheated well in the microwave the next day. It's adapted from a Delia Smith recipe.