Marinate chicken in pickle juice and hot sauce for at least 4 hours (or overnight if possible).
To make the special sauce, combine the mayonnaise, ketchup, black pepper, Worcestershire sauce, and garlic powder. Adjust any seasonings, if desired. Refrigerate until ready to serve.
To make the chicken, fill a Dutch oven or cast iron pot with 3 to 4 inches of peanut oil. Heat the oil to 375 degrees F, keeping a close watch on the thermometer, making sure not to exceed this temperature.
While the oil is heating, prepare the batter. Combine the flour, cornstarch, salt, paprika, baking soda, and cayenne in a large bowl. Add the egg whites, canola oil, and pickle juice and whisk until the mixture is thick and sticky (almost like glue). Stir the marinated chicken into the fry batter until every piece is completely coated.
Working in batches, fry the chicken until crisp and golden brown, 2 to 3 minutes per batch. (The coated chicken pieces will want to clump together in the oil, so I like to put in each piece one by one.) The oil temperature will drop to approximately 350 degrees, which is the temperature you should maintain while frying. Return the oil to 375 degrees in between batches.
Using a spider, remove the cooked chicken to drain on a sheet pan lined with paper towels or a large brown paper bag. When all the chicken is fried, return oil to 375 degrees. (Taste chicken. If desired, drizzle additional pickle juice over chicken when it comes out of the fryer for a more predominant "pickle" flavor before continuing with second fry.)
Add ALL of the fried chicken back into the hot oil for 30 seconds to 1 minute. The second fry will not only re-heat the chicken but make it extra crispy. Remove the chicken back to the sheet pan lined with fresh paper towels or a large brown paper bag. Season generously with kosher salt.
Serve warm chicken immediately with the special sauce. If serving as an appetizer, you can put a toothpick through each piece. Reheat the chicken in the oven, if necessary.