Cover the bottom of a fish poacher with the white wine and water. Chop the potato, carrot, onions, and celery into thin slices that will fit neatly and evenly under the rack. Add the spices. Grease the rack with a bit of olive oil or butter so that the skin and fatty tissue does not stick to it. Place the salmon on the rack and put on the poacher lid. Cook over a medium flame, straddling two stove burners, if necessary, for about 10-14 minutes, or until a small cut into various portions of the flesh prove that the inner portion of the fish is not still raw.
Prepare a large platter lined in the center with bib lettuce or some other soft, leafy green. Arrange elongated cucumber slices into a decorative shape at each end. Place the salmon on top of the lettuce and spoon the sauce down its center. Place a few thin radish slices like buttons down the length of the fish for decoration. Serve immediately.
While the salmon is poaching, make the Mousseline Sauce. Beat the egg yolks and the lemon juice together at high speed until a pale yellow. Pour in the hot butter (it must be boiling; a microwave will quickly make it so), and add the salt and Cayenne. Cool slightly. Add the whipped cream a bit at a time, stirring constantly.