I've never seen just a dessert buffet, but there is many great places for dessert at disney. The main street bakery in MK has great desserts, as well as the different countries in world showcase and Ghiradelli's in Downtown disney has great sundaes as well as beaches and cream. Linda
I'd second Boma, they have incredible desserts. The oreo bon bons at Cape May are outstanding. You also should check out Goofys Candy Kitchen in DTD the desserts there are to die for ~ make your own chocolate dipped apples, pretzels, cookies or marshmallows. As well as tons of other treats. Its my hubbies favorite snack place!!
No kidding! Sweet pretzel, choc mousse cake, school bread...ahh! My last trip was one big dessert buffet. I even ate a cookie icecream sanwich from Main St. Bakery- 2 big cookies and 3 scoops of icecr. I seriously felt ill after that. I can't wait to do it again either! I never learn. I have a serious sweet tooth!
Though overall we loved the meal at Boma, I thought the dessert selection was pretty weak. Certainly if the Zebra domes are your thing you'll be in heaven, but I found the offering narrow and unappealing. So I actually ate more soup and veggies instead. I had a Mickey bar while we were at AK that day so it wasn't as if I hadn't had my "treat" for the day.
Some of the buffets have pretty good dessert sections. The Crystal Palace had a good one last time I was there, the Biergarten had some nice offerings dessert-wise as well.