Place the salmon in a bowl and cover with 1/2 bottle of champagne. Marinate it like this for a whole day, or overnight. If you're short on time, marinate for 1-2 hours. Now, if you're wondering "won't marinating overnight cook the salmon" -- the answer is nope. As long as you're marinade doesn't have citrus or vinegar, you're good to go for leaving the salmon in it overnight.
Make the Sauce Verte: In a medium bowl add all the ingredients. At high speed, beat with electric beater until smooth. You can also make the sauce in a blender if you like a smoother, creamier consistency.
Refrigerate, covered, for at least 2 hours before serving. You can also make the sauce a day ahead which is ideal to give all the flavors a chance to blend together. Makes about 1 1/4 cups.