For the slaw: Whisk together the mayo, pickle juice, garlic and hot sauce to taste in a large bowl. Add the cabbage, jalapenos, parsley, pickles and scallions, stirring to combine. Cover and refrigerate until using.
For the chicken: Whisk the flour, pepper, garlic salt, paprika and kosher salt in a shallow bowl. Pour the buttermilk into another shallow bowl.
Dredge one piece of chicken at a time in the flour mixture, shaking off excess. Dip in the buttermilk, allowing excess to drip back into the bowl. Dredge again in the flour mixture, shaking off excess. Set aside onto a tray lined with wax paper. Repeat with all of the chicken.
Fill a large heavy skillet with 1/2 inch of oil. Heat over medium heat until a deep-frying thermometer inserted in the oil reaches 350 degrees F. Fry the chicken until golden brown and cooked through, 5 to 6 minutes per side. Transfer to a wire rack set over a baking sheet and season with additional salt.
To assemble: Butter the rolls. Heat another large skillet over medium heat. Toast the rolls buttered-side down until browned and crisp, about 1 minute. Build the sandwiches on the rolls with the chicken and slaw.