Place mandolin over a medium glass bowl of water. Slice potatoes into very thin rounds into water. Let stand for one hour.
Rinse potato slices and lay out on a clean kitchen towel or paper towels to dry.
Line a rimmed baking sheet with a cooling rack and set aside.
Heat four centimeters of oil in a large, heavy-bottomed pot or Dutch oven to 300°F (148°C).
Fry potatoes in batches until golden brown and bubbles disappear, about two to three minutes. Adjust heat up or down to maintain oil temperature during cooking. Remove potato chips from oil to prepared baking sheet and sprinkle with seasoning powder while still hot.
Make ahead: Chips can sit and stay crispy at room temperature for up to two days loosely covered.