Trim chicken breasts and slice each in half horizontally to make 4 cutlets (or butterfly and pound to 1/2-inch thickness). Combine buttermilk, 1 tsp kosher salt and 1/2 tsp black pepper in a shallow dish. Add chicken, coat, cover and refrigerate for at least 20 minutes (up to 4 hours).

Mix Dry Coating

In a large shallow bowl, whisk together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper and a pinch of salt until evenly combined.

Dredge and Fry

Heat vegetable oil in a heavy skillet over medium-high until it reaches 350°F (or a drop of batter sizzles immediately). Remove chicken from buttermilk, letting excess drip off, then dredge thoroughly in the flour mixture, pressing to adhere. Shake off excess. Fry cutlets in batches 3-4 minutes per side, until golden brown and internal temperature reads 165°F. Transfer to a wire rack set over a sheet pan to drain and keep warm.

Make Spicy Mayo

Whisk together mayonnaise, hot sauce, lemon juice and 1/4 tsp salt in a small bowl. Taste and adjust heat or seasoning. Refrigerate until assembly.

Prepare Slaw

In a medium bowl combine shredded cabbage, carrot and green onion. Whisk together apple cider vinegar and sugar until sugar dissolves, then toss with the cabbage mixture. Season to taste with a little salt and let sit 5-10 minutes to soften and marry flavors.

Toast Buns & Assemble

Heat a skillet over medium heat and melt butter. Split brioche buns and toast cut sides in butter until golden, about 1-2 minutes. Spread 1 tablespoon of spicy mayo on each toasted bun bottom. Place a fried chicken cutlet on each, top with a generous handful of slaw and 2 pickle slices (or more to taste). Spread a little mayo on the top bun and close sandwich. Serve immediately.

Finishing & Tips

If preparing ahead, keep fried chicken in a low oven (200°F/95°C) on a rack to retain crispness for up to 20 minutes. For extra crisp, double-dip the chicken: after first dredge, briefly dip back in buttermilk and re-coat in flour mixture before frying. Adjust cayenne and hot sauce for preferred heat level.