I've borrowed Judy's sourdough bread recipe, quoted below, so that I can give you this variation that I came up with. It makes a beautiful golden loaf. Be sure to visit her blog, Recipes from a Southern Country Cook for some wonderful cooking ideas.
I've put my additions in italics. The rest is quoted from Judy's blog.
1 cup sourdough starter
1 1/2 cups warm water
1 1/2 teaspoons salt
1/2 cup white sugar
1/2 cup corn oil (can use vegetable or canola)
1 cooked, peeled, mashed sweet potato
6 cups all-purpose flour (you'll need to add an additional cup or two of flour, depending on the size of your sweet potato)
Mix sugar, oil, salt, water and starter, and mashed sweet potato in a large bowl. Add flour. Turn out onto floured surface and knead several times until forms a ball adding flour if needed. Place the dough into a large, oiled bowl, turn once so that dough will be greased, cover with clean dish towel and let rise overnight.
The next day, punch the dough down, turn out onto floured surface, knead for several minutes, divide in half, place in 2 (or 3) greased bread pans. Cover and let double in size. Bake at 350 degrees for 40 to 45 minutes or until golden brown. Turn out to cool.