This traditional salmon dinner can be served with a citrus mustard mayonnaise for a twist on a classic dish.
Make court-bouillon by combining 5 quarts water, 2 1/2 cups wine, bay leaves, celery, onions, carrots, parsley, peppercorns, salt, and lemons in a large fish poacher with rack in, at least 24 inches long and 4 1/2 inches deep. Cover; bring to a boil. Reduce to a simmer; cook 30 minutes. Turn off heat, and let cool for 15 minutes.
Cut a length of cheesecloth into three 34-by-18-inch pieces, and overlap them to create a 30-by-34-inch-wide piece of cheesecloth. Rinse salmon with cool running water; pat dry. Wrap salmon in cheesecloth, tying the ends closed with kitchen twine, and tying loosely once around the middle. Using ends as handles, place salmon into poacher, and add enough water to just cover salmon.
Cover; bring to bare simmer over medium heat. Poach salmon 30 minutes. Lift rack enough so fish is slightly raised out of water; poke an instant-read thermometer into back of widest part of fish. Salmon is done when internal temperature reads 135 degrees, which may take up to 1 hour. Turn off heat; let stand in poacher 15 minutes. Lift rack with salmon out of water and onto large platter. Do not unwrap salmon or remove from rack; let cool to room temperature, about 1 hour.
To make aspic glaze, strain 10 cups court-bouillon through fine sieve lined with cheesecloth into large stockpot. Add egg whites and remaining cup wine. Whisk over medium heat until mixture begins to simmer, about 10 minutes. Stop whisking, and let simmer 15 minutes more, or until broth is clear and all the foam has risen to surface. Remove foam with slotted spoon, and strain broth through very fine sieve lined with double thickness of cheesecloth, which has been soaked in ice water and wrung of excess.
Transfer broth to large saucepan. Bring to boil, reduce to simmer, and cook until reduced to 4 1/2 cups. Meanwhile, sprinkle gelatin over 1/4 cup cold water in small bowl; let stand 10 minutes. Warm gelatin over gently simmering double boiler; stir until dissolved. Stir into broth; transfer to large bowl. (The less gelatin used, the better.)
When salmon has cooled, gently turn bottom side up. Unwrap; do not remove cheesecloth. With dull side of paring knife, scrape off skin, and remove brown fatty bits underneath. Using cheesecloth to cradle salmon, turn the presentation side up; repeat skinning process. Remove and dispose of cheesecloth. Transfer salmon, still on rack, to refrigerator. When chilled, thicken aspic glaze by stirring over ice bath. Aspic should just be thick enough to coat; if it thickens too much, stir it over a double boiler until viscous again.
Arrange salmon (still on rack) on metal rack over baking sheet. Ladle 1 1/2 cups aspic over salmon to coat. Chill salmon 20 minutes; repeat glazing process. While salmon chills again, put thin layer of aspic in bottom of serving platter. Carefully transfer salmon from poaching rack to the platter. Decorate salmon with your choice of garnishes, temporarily securing citrus slices with toothpicks. Over each garnish ladle a little aspic; chill once more. Remove toothpicks before presenting.