Instructions

1. Boil the potato chunks until a knife slides through without any resistance. Undercooked potato will not blend to a paste, and every lump left in the mixture becomes a pale raw spot on a finished chip.
2. Drain them properly and let the steam come off for a minute before the sour cream goes near them. Water clinging to hot potato thins the paste and adds hours to the tray time.
3. Blend the potato with the sour cream, water, onion powder, minced onion, parsley, salt and pepper until it is completely smooth. Any fleck of unblended onion sits proud of the sheet and scorches before the rest is anywhere near dry.
4. Spread the paste on lined trays as thinly as you can while keeping it even — a skim you can almost see the liner through. Thickness decides the snap of these entirely, and a heavy patch dries into a chewy disc.
5. Score the sheet into chip-sized pieces before it goes in. A dried sheet shatters at random, and random shards have no flat edge for a dip.
6. Dry at 63 °C for 5 hours, then carry on at 63 °C for 5 hours, and longer again if the sheet still gives anywhere. The sour cream puts far more water in than a plain potato chip carries, so a long run is normal rather than a sign of a problem.
7. Peel a piece off and let it cool in your hand before judging it. Warm potato is always limp, and cooling is what reveals whether you have a chip or a leathery thing pretending to be one.
8. Break the sheet along the score lines and jar the chips with the lid tight. Dairy and starch together will not sit around — three weeks is the honest limit, and any chip that has gone bendy can be crisped back on a warm tray.