To make the chicken
Place the chicken in a plastic freezer bag and pound lightly, until it's an even width. Add the buttermilk to the bag, massage until coated, seal the bag and refrigerate at least 4 hours or overnight.
Preheat the oven to 400F and prep a sheet pan with a light coating of butter.
In a shallow bowl, mix the flour, spices, and cornflakes together until evenly combined. One at a time, remove the chicken from the buttermilk marinade and dredge completely in flour mixture, shake off any excess, and place on the baking sheet. Brush the tops of each breast with the melted butter.
Bake for 25-35 minutes or until golden brown and crispy, and the chicken is cooked through.
To make the slaw & spicy mayo.
Slaw: Add lime and honey to a bowl and stir until combined. Add the remaining ingredients and toss to coat. Season with salt and pepper if desired.
Mayo: Add hot sauce, cayenne and mayo together in a bowl, stir until combined.
To assemble the sandwich
Spread either side of a split bun with a generous helping of spicy mayo. Add a chicken breast to the bottom half, top it with 2-3 tbsp of slaw and pickle slices, and the top of the bun.