Preparation

• Make the chicken: One at a time, place the chicken breasts in a resealable freezer bag; using a meat mallet or rolling pin, pound them to an even ¼-inch thickness. Cut each pounded breast in half.
• Pour the cold water into a medium bowl; add the 2 tablespoons of the salt and the sugar and whisk until dissolved. Place the chicken breasts in the brine, cover the bowl, and refrigerate for at least 4 hours or overnight.
• Line a plate with a few layers of paper towels and set it next to the stove. Pour the oil into a large, high-sided pot or Dutch oven until it reaches a depth of about 1 inch. Heat the oil over medium-high heat until shimmering.
• In a medium bowl, whisk the egg and milk until evenly combined.
• In another medium bowl, whisk the flour, cornstarch, baking powder, garlic powder, pepper, Accent, paprika, and the remaining ¾ teaspoon salt. Drizzle 4 tablespoons of the egg mixture into the flour mixture and mix with a fork until the flour mixture is evenly clumpy.
• Line a baking sheet with aluminum foil for easy cleanup. Remove the chicken from the brine and pat dry with paper towels. Dip each breast into the egg mixture, then into the flour mixture, pressing firmly so that the clumps adhere. Set the breaded chicken on the lined baking sheet.
• Carefully place a few pieces of breaded chicken into the hot oil without crowding the pot. Cook until golden brown and crispy on both sides, 4 to 5 minutes total. Place the cooked chicken on the paper towel-lined plate to drain.
• Make the sauce: In a small bowl, whisk together the mayonnaise, barbecue sauce, and mustard.
• Assemble the sandwiches: Spread some of the sauce on each top and bottom bun. Top each bottom bun with a piece of crispy chicken and a few pickles. Close the sandwiches and serve immediately.