In a medium bowl, combine the buttermilk, salt, pepper and hot sauce. Add the chicken thighs and marinate in the fridge for at least an hour or overnight.
Prepare the coating. Whisk the flour with the salt, pepper, garlic powder, paprika and cayenne powder. Prepare the siracha mayo by combining the mayonnaise and siracha. Stir until well blended.
Working one piece at a time, dip each marinated piece of chicken into the flour, making sure both sides are completely coated. Set aside.
Fill your Dutch oven or cast iron pan with enough oil to reach about ½ inch high. Heat the oil until it reaches 350°. If you don’t have a thermometer, dip a wooden spoon or small piece of bread in the oil. If it bubbles, the oil should be hot enough.
Fry the chicken in the oil for about 3 minutes per side until cooked through. Do not overcrowd the pan. If your pan isn’t big enough, fry two at a time. When done, the thickest part of the chicken should read 75° C (165° F). If you don’t have a meat thermometer, cut one piece open at its thickest part and check for doneness. When done, rest the chicken on a wire rack.
Spread some siracha mayonnaise on toasted sides of buns. Top with pickles, fried chicken and slaw or lettuce.