Cut the potatoes into thick wedges; keep the skins on.
Soak wedges in ice water for 20 minutes to remove excess starch.
Drain and pat the potatoes very dry with towels.
Stir buttermilk and hot sauce in a bowl. Toss in the potatoes to coat.
Whisk flour, cornstarch, baking powder, salt, paprika, garlic powder, onion powder, and pepper in a shallow dish.
Dredge buttermilk-coated wedges in the flour mix, pressing to help the crust stick. Set on a rack.
Heat the oil in a deep pot to 350°F over medium heat.
Fry wedges in batches for 5–7 minutes, turning, until golden and crisp and the centers are tender.
Drain on a rack or paper towels and sprinkle with a pinch of salt. Serve hot.