If your Mom is an old lady from the southeastern states, you have probably eaten this stuff around christmas. It is mouthwringingly sweet, and has a very peculiar texture which is at once chalky and creamy, kind of like fondant. It has peanut butter in it.Yes, it is made with a potato. There are lots of recipes online for it, but I still have no idea what the origin of the recipe could be. It's one of those things where you think about it and go 'Seriously? Who does that?'
1 baked russet potato
2 lbs powdered sugar, more or less
1 tsp vanilla
Peel and mash the potato. Add the vanilla and half the sugar. Mix until smooth, then gradually add more sugar until you have a stiff, rather sticky dough.
Roll the dough out between sheets of waxed paper until it is 1/8" thick, then spread a thin layer of peanut butter on it. Roll the dough up into a rope, then cut it into slices.
That's really it, but there is some stuff that is useful to know:
1. You can microwave the potato, but I think it would be better to actually bake it.
2. That's because you want to have the mashed potato be fairly dry, and also the baking will make a more pronounced potato flavor. It is Potato Candy, after all.
3. Even so, the first few cups of sugar will melt into a soup right away. That's normal. Just keep adding more.
4. Making a drier dough will make it less sticky, but it will be harder to roll out that way.
5. As you roll it out, peel the paper off the dough and rotate it frequently. It will come out smoother that way.
6. Roll slowly and gently. Violent treatment will cause the dough to resist handling.
One of the most interesting characteristics of this stuff is the handling property of the dough whereby it behaves like a solid and breaks into chunks if you cut or twist it, but it will ooze slowly through your fingers if you squeeze it gently. If you've ever played with cornstarch and water, or sand on a beach, the principle is the same. There is some cornstarch in powdered sugar, but that isn't what's making it behave that way.
When you first put the sugar in the mashed potato, the tiny sugar particles rapidly dissolve in the moisture from the potato. Eventually, the small amount of water present will no longer be able to dissolve any more sugar, and the sugar particles will remain intact, suspended in liquid, just like raw cornstarch (which is insoluble) in water. There is some kind of fancy physics explanation for why particles suspended in liquid behave that way, but I don't know what it is. I think it has to do with surface tension, but I could be totally wrong, so don't rely on me about that.
I only make this stuff about once every 4 or 5 years because I have to have forgotten that my sweet tooth is not powerful enough for me to want to eat more than 3 pieces of it. I did have one more incentive this time though: I bought a vintage potato press. It's totally neato. You fill the removable can with cooked potato, crank the handle down, and it instantly extrudes a whole recipe worth of perfectly mashed potato. I doubt it will see much use for potato candy in the future, but I do want to try making lefse. If I get up the nerve, I'll tell you about it.