In a large bowl, whisk together buttermilk, egg, and Cajun seasoning until well combined. Submerge chicken in marinade and cover with plastic wrap. Marinate for at least 1 hour or overnight.

In a separate bowl, combine flour, cornstarch, baking powder, and remaining Cajun seasoning. Coat marinated chicken in the flour mixture.

Heat oil in a deep skillet or fryer to 350°F (180°C).

Fry the chicken for about 4-5 minutes per side until golden brown and cooked through. Drain excess oil on a wire rack.

Toast the buns lightly on a griddle or in the oven.

Assemble the sandwich by spreading mayonnaise on the bottom bun, placing the fried chicken, drizzling jalapeño honey, and topping with the other half of the bun.

Serve immediately with sides of your choice.