In a large bowl, whisk together buttermilk, pickle juice and Sriracha.
In a gallon size Ziploc bag or large bowl, combine chicken and buttermilk mixture; marinate for at least 4 hours to overnight, turning the bag occasionally.
In a large bowl, whisk together flour, cornmeal, baking powder, cayenne pepper, 2 teaspoons salt and 2 teaspoons pepper.
Working one at a time, remove chicken from buttermilk mixture and let excess drip off. Then dredge in flour mixture, dip into buttermilk mixture, then dredge again in flour mixture, pressing to coat.
Heat vegetable oil in a large stockpot or Dutch oven over medium high heat until it registers 360 degrees F on a deep-fry thermometer.
Working in batches, add chicken and fry until golden brown, turning occasionally, about 4-5 minutes. Transfer to a baking sheet fitted with a wire rack and keep warm.*
In a small bowl, whisk together mayonnaise and Sriracha.
To serve, spread buns with Sriracha mayonnaise, then top with chicken, coleslaw, and pickles.
Notes
*The chicken can be kept warm, as needed, in the oven at 200 degrees F.