1. Slice the chicken in long strips; you should have at least 3 strips per breast.
2. Put the buttermilk, salt, hot sauce and rosemary in a resealable plastic bag and add the chicken. Marinate, refrigerated, for 20 minutes or up to 2 hours.
3. Preheat the oven to 95°C and place a cooling rack on top of a baking sheet. Pour enough rapeseed oil in a shallow cast-iron skillet so it will cover the chicken generously (estimate it). Heat the oil over medium-high heat.
4. For the coating, add the flour and some salt and pepper to a shallow bowl. In another shallow bowl, beat the eggs with 1 tablespoon water. Mix the crushed chips with the panko in a third shallow bowl.
5. Remove the chicken from the marinade and pat dry with a paper towel. Working one at a time, dip the chicken strips first into the flour mixture, shaking off any excess. Then dip into the egg, allowing the excess to drip off, and finally, into the potato chip mixture.
6. Place the chicken strips in the hot oil and cook thoroughly, 7 to 10 minutes. Do not overcrowd your pan; fry the chicken in batches if need be. Transfer the cooked chicken to the prepared cooling rack and keep warm in the oven until ready to serve.