The way I do it is en croute. Chop up some stem ginger(the one in jars in syrup), add a handful of currants and mix this into butter. Lay a piece of ready rolled puff pastry out place a fillet of salmon on it. Spread the butter mix over the fillet and then make a parcel making sure of no chance of leakages. Egg wash and bake.
I would use the creme fraiche as a complement to the finished dish by mixing in the juice and zest of a lime and some black pepper. This gives a nice balance with an acidic zing to complement the richness of the salmon.
I do this with individual salmon steaks rather than a whole fillet for ease and bake at 200c for 25 minutes, be careful not to overcook.