Water Grill (call to check if it's still offered: http://static.flickr.com/143/324645733_902c5b8cd5.jpg
If you want, these places offer huge dessert sampler/platters shareable by two or three people:
Saddle Peak Lodge:
Whist at the Viceroy: http://static.flickr.com/138/324645732_19bb8a4a74.jpg
Matsuhisa/Nobu - if you ask for several desserts, they'll combine it prettily all on one huge plate.http://static.flickr.com/142/324645739_5df63fc864.jpg
I've also requested a single-plated dessert tasting at Patina: http://static.flickr.com/143/32464721...
Have fun and report back!
There are specific times that you can make reservations for the dessert tasting at Providence, they are listed on Opentable. You could try calling the restaurant to check if they will accept a reservation for a different time.
**Dessert only reservations accepted exclusively at the following times: Monday through Friday at 6:00pm or 10:00pm
Saturday 5:30pm, 6:00pm, or 10:00pm
Sunday 5:30pm, 6:00pm or 9:00pm