Potato Candy Pinwheel

1. Boil the cubed potato in salted water until completely tender, about 12 to 15 minutes, then drain very well and mash until smooth with no lumps; let it cool until just warm.
2. Beat the softened butter, vanilla and a pinch of salt into the warm mashed potato; you should have roughly a quarter cup of starchy paste that will dissolve a surprising amount of sugar.
3. Add the powdered sugar one cup at a time, beating after each addition; the mixture will look wet at first then suddenly come together into a stiff, smooth dough, so stop adding sugar once it is firm enough to roll.
4. Sprinkle a work surface generously with powdered sugar and roll the dough into a rectangle about a quarter inch thick, dusting the rolling pin to prevent sticking.
5. Stir the cinnamon and nutmeg into the peanut butter, then spread it evenly over the dough, leaving a thin border along one long edge.
6. Starting from the long side opposite the bare border, roll the dough up tightly into a log, pressing the seam to seal, then wrap in parchment and chill until firm, at least one hour.
7. Slice the chilled log crosswise into pinwheels about half an inch thick with a sharp knife and serve; store any extra in an airtight container in the refrigerator.

You'll use: Large pot · Saucepan