How to Make It
Stir together pickle juice and granulated sugar in a shallow dish until sugar dissolves. Add chicken breasts; cover and chill 40 minutes. Remove from brine, and pat dry.
Whisk together buttermilk, cayenne, and egg in a second shallow dish. Whisk together flour, cornstarch, powdered sugar, powdered milk, salt, pepper, paprika, baking powder, and baking soda in a third shallow dish.
Dredge brined chicken in flour mixture to coat, and shake off excess. Toss chicken in egg mixture to coat, and then back to flour mixture to dredge again. Press flour mixture to adhere to chicken, and place on a wire rack. Chill 15 minutes. Heat oil to 325°F in a medium saucepan over medium-high.
Carefully add chicken breasts to hot oil, 1 at a time, turning occasionally, until cooked through, 4 to 6 minutes. Let drain on a wire rack set in a baking sheet lined with paper towels.
Heat a large nonstick skillet over medium. Spread butter evenly on cut sides of buns. Place buns, buttered side down, in skillet; cook until toasted, about 30 seconds. Place 2 pickle chips on each bottom bun, and top with chicken and bun top. Wrap each sandwich in a piece of aluminum foil, and let stand 3 to 5 minutes before serving.