You could take a standard stout recipe and treat the sweet potatoes like you would in a pumpkin beer. Just skin them, cube them, and roast them at 350 in the oven for an hour then add them to your mash or put them in the boil. I'm not sure about replicating the Lazy Magnolia beer though as I'm not familiar with it. I would like to get my hands on some though, it sounds tasty. Probably not going to happen though as I'm pretty far north and the distributors don't seem to carry it.