Instructions

1. Tip the cranberries into a bowl of water and skim off anything that floats oddly or feels soft. A cranberry that has gone past it is pale and squashy, and one of those will ferment in the jar.
2. Pour boiling water over them and leave them a few minutes. The skin is waxy and waterproof, and until it splits, nothing gets out of the berry at all.
3. Listen for the popping to stop, then pierce any berry that is still whole with a pin. One unsplit berry stays completely raw inside while everything around it dries.
4. For sweetened craisins, dissolve one part sugar in two parts water and toss the split berries through it. The syrup replaces some of what the drying takes out and keeps them pliable; skip it and you get something considerably sharper.
5. Drain them well and space them about 13 mm apart on the trays. Cranberries stick to each other as the syrup concentrates, and a clump comes off as one solid lump.
6. Dehydrate at 57 °C for 13 hours, giving the trays a shake every few hours to stop the undersides flattening and sticking.
7. They are done when a berry is wrinkled and leathery and no juice appears when you squeeze one between your fingers. A cooled berry that still feels plump in the middle is not finished, whatever the clock says.
8. Cool them, then condition them in a loosely closed jar for a week, shaking it daily, and put the lot back on the trays if the glass fogs. After that they will sit in a sealed jar in the dark for a year, and the sweetened ones a little less.