To make the burgers, place all of the dry ingredients in a large ziploc bag and shake well (alternatively, mix them in a bowl).
Dip the chicken breasts in the buttermilk then place in the bag. Shake well to coat the chicken with flour and spices. Place the coated breasts on a tray lined with greaseproof paper and let rest 30 minutes.
Heat a deep fryer or saucepan with vegetable oil until very hot. Add chicken and deep fry until cooked through. A medium thickness breast will take about 10 minutes. Once cooked, remove from oil and drain on kitchen paper towels.
Meanwhile, make the corn relish. Mix the corn with the mayonnaise and salt and pepper to taste. Roughly puree with a hand blender if desired.
To serve, lightly toast the hamburger buns. Place the chicken in a bun, top with the corn relish then remaining garnishes.