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, trimming off pointy ends as necessary.
• 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 paper towels and set next to the stove. Pour the oil into a large pot until it reaches a depth of about 1 inch. Heat the oil over medium-high heat until shimmering (about 350°F).
• 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 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, letting excess drip off, and then into the flour mixture, pressing firmly to adhere. Set on the lined baking sheet.
• Carefully place pieces of breaded chicken into the hot oil without crowding. Cook for 4 to 5 minutes until golden brown and crispy. Place 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 sauce on each bun, top with crispy chicken and pickles. Close and serve immediately.