Which shoofly pie would that be? Recipes and even names are legion, and that's just in cookbooks. It doesn't begin to take into account the instant-gratification/instant-confusion provided by the Internet.
There is some nonsense on the Internet that the name may be a bastardization of the French soufflé, to which shoofly pie bears not a hint of resemblance. There is also some musing that you had to shoo the flies away from its molassesy sweetness, which, if you know anything about flies, you would certainly have to do. But the name also did not come from that necessity.
William Woys Weaver, author of the delicious Pennsylvania Dutch Country Cooking, says the pie was introduced at Philadelphia's Centennial International Exhibition in 1876 as the Centennial Cake.
Recipes for the cake/pie were shared for years afterward, but it was the alternate names that stuck – Granger Pie and Shoofly Pie. Weaver says the word shoofly comes from the brand name of the molasses called for in the original recipe. Soufflé indeed!
Nowadays, shoofly pie recipes are all over the map. "Dry-bottom" pies are built on a soft gingerbread crust. One variation we saw solemnly says that you transform a granger pie into a shoofly pie by sprinkling raisins over the bottom of the crust. Some omit eggs. Some include chocolate. According to Weaver, what matters is the molasses. No molasses, no shoofly pie. Simple as that.
We feel very confident that this is the original Shoofly Pie recipe (when has William Woys Weaver ever lied to us?*). He says his grandmother obtained the Centennial recipe in the early 1930s from Mrs. Miles Fry of Ephrata, Penn., whose family had preserved it from the 1870s. But there are those in the South who lay claim to the shoofly pie, and there are those who would trace its roots to the Banbury or chess pies of England. But at some point you have to put your foot down!
You did ask a question, didn't you? Oh yes, there is no reason why you can't freeze a shoofly pie. Bake it before freezing, or the baking soda will not get its chance to react with the acidity of the molasses before it loses its potency.
*Well, after pointing us toward the molasses brand as the inspiration for the pie's name, Weaver cheekily includes an old-time flyswatter in the photo for Shoofly Pie in his book. Certainly he had a good laugh over that one!