If you are looking for French Christmas dinner in the Tokyo area, the Grand Hyatt is offering it's annual French dinner in its French restaurant:
http://restaurants.tokyo.grand.hyatt.com/french-kitchen-tokyo/news/20111222140308.html
[quote]
Christmas Dinner 2011
Period?22 ? 25 December
5?30 pm ? 9?30 pm
An all-day dining restaurant offering traditional bistro dishes stylishly arranged. The restaurant features the Chef's Table - a private dining room equipped with a kitchen - ideal for private parties and company celebrations during the holiday season.
Christmas Dinner 2011
?16,000 / ?20,000
* Kindly note that all prices are subject to a 10? service charge.
Phone: 03-4333-8781
Hours: Daily 6:30am - 9:30pm
Bar 11:30am - 9:30pm
Location: 2F
# of seat: 264
Private Dining Room: Chef's Table (10 people*) Wine Table (12 people) Terrace Table (6 people)
* Layout can be changed; maximum of 20 people[/quote]