updated by @sally-cook: 04/12/15 01:32:36AM
There have been discussions of this issue on the eGullet forum, such as this one: http://forums.egullet.org/topic/87881-chocolate-champagne/?hl=%2Bchampagne+%2Btruffle#entry1775172
The conclusion was that using champagne itself is rather difficult, and most people use marc de champagne, which according to one writer on that site is a very concentrated flavoring "gel" which pours and smells very strongly of wine.
But according to another link, Jacques Torres makes a champagne truffle, with the following description: "Jacques' Champagne Truffles, filled with Champagne Taittinger, are a mouth-watering combination of milk chocolate, fresh cream and Taittinger Brut La Franaise champagne. These champagne truffles rise above the rest due to their inclusion of real champagne. These are one of the few champagne truffles to do so."
Lorraine oils has a champagne oil that tastes very much like champagne - http://shop.lorannoils.com/chocolates/super-strength-flavors