Parboil: start in cold salted water, bring to boil, cook for 5-6 minutes.
(Optional) Baking soda: add a pinch to the boiling water. Alkaline environment breaks down surface pectin, creating a rough starchy exterior. More texture = more crunch.
Rough up: drain, return to pot, shake vigorously until edges are ragged and fluffy.
Dry thoroughly: moisture kills crispiness.
Coat in thin layer offat: toss well so every rough surface is coated.
Don't crowd: single layer with space between pieces. Crowding = steaming.
No lining: roast directly on metal. Parchment or foil traps steam.
Roast at 200 °C until golden and crisp (40+ minutes).