Place mandolin over a medium glass bowl of water. Slice potatoes into very thin rounds into water. Rinse potatoes and refill bowl with water. Let stand for 1 hour.
Rinse potatoes 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 1-1/2 inches of oil in a large, heavy-bottomed pot or Dutch oven to 300F (148C)
Fry potatoes in batches until golden brown and bubbles disappear, 2 to 3 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 up to 2 days loosely covered.