WHile I think it's great that you want to make a certain dessert before you go.....and while as I said, finding those PARTICULAR desserts at WDW may be tricky....there is no shortage of fabulous desserts at WDW!
If you will be dining at any signature locations, the desserts are often the highlights of the meals. At the signature locations, (think 2 credits on Dining Plan) the options change seasonally, so there's little point in any of us saying what was in a given location on a given date, cuase the choices are likely to change before you go.
Another place that comes to mind is Kouzzina. Kouzinna is Cat Kora's place at the Bwk. It's not fully 'southern' it's Greek/Southern fusion cuisine - but especially come the holiday's it may well have offerings that are to your liking.
If it's yummy desserts onthe go you crave: consider these fine locations: Main ST Bakery, Starring ROlls in HS, Kringla Og Bakery in Norway in Epcot, The France bakery In Epcot (I usually prefer Norway myself, but both have tasty treats), the Boardwalk Bakery, The Villians shop in HS (Small treat area, but some yummy treats), The Goofy Candy place in DTD, the 'CAndy Cauldron in DTD (Sucha cute theme), at any ice cream cart - get a Mickey Bar! Mickeybar: And those are just a few....
Around Thanksgiving, many places are likely to have special Christmas holiday offerings available. A fun special place to try is the gingerbread house in the Grand Floridian! It is big enough to be a small gift shop!