You have to book this with the Disney Group Sales Department.
I got a fax from them last Friday. Here's the info about the dessert reception.
Booking Guidelines
Dessert Reception menus start at $17.50++ per person
Minimum of 20 guest. Maximum capacity is 300 guest
Theme park admission is required
You must have a contracted group room block at a WDW Resort to host this special event
Enhancements(prices available upon request)
Enjoy International Coffees and Cordials with your delectable dessert selection
Capture the moment with a Disney photographer
Menu
Florida Lemon Bars
Double Chocolate Brownies
White Chocolate Chip with Macadamia Nut Cookies
Oatmeal Raisin Cookies
Chewy Rice Crispy Treats
Chocolate Marshmallows Squares
Coffee, Hot Tea, Lemonade
$17.50 pp
(1 hour, 20 person min.)
I also have one for Fantasmic. You have to book at least 10 rooms in order to schedule one of these.
Several families from my son's school are trying to plan a trip to Disney together this summer. If we can get 10 rooms, I want to book both dessert parties.