Elegant Venue.....Excellent Food..... The Orangery
If I were you, I'd look into RT Lodge in Maryville. The chef has great credentials and the affiliation with Blackberry Farm implies good things.
No guarantees, but it's the most interesting place I've heard of.
There are some other very rural destinations (one near Paint Rock over west/south of Kingston ) which may not have the elegance you want.
A venue that is by request only is at the top of the (used to be) Marriott downtown (the one that looks like TVA built a dam and missed the river).
When it first opened, one of the top floors was a dining room with a view to the Smokies. I wanted to have a small wedding reception there, but it was only for 15 and they required a larger number of patrons to use it. It would be a special place for locals who have never seen that venue.
Not that many places have rooms for 40. The Foundry down town and Rothchild's Catering do have that room size. I don't know what Ruth's has.
Not elegant, but Puleo's at Strawberry Plains has a room that can handle 40. Naples also has a back room that can handle 40; going off of their menu and letting their chef be creative can be a wonderful surprise.