Rinse the chicken breasts and pat dry. Trim any visible tendons or cartilage. Place them in a sealable container or zip-top bag.

Add the buttermilk, paprika, and garlic powder. Seal and shake to coat. Refrigerate for at least 30 minutes, preferably overnight.

Crush the cornflakes into coarse crumbs (use your hands or a bag and rolling pin). In a shallow dish, combine the crushed cornflakes, all-purpose flour, and baking powder. Mix well.

Pour the remaining 3/4 cup buttermilk into a separate shallow dish.

Remove the chicken from the marinade, letting excess drip off. Dredge each piece first in the cornflake mixture, then dip into the buttermilk, and dredge again in the cornflake mixture, pressing gently to adhere. Set aside and let rest at room temperature for 10 minutes.

In a large skillet or Dutch oven, heat about 1 inch of vegetable oil or clarified butter to 325-340°F (163-170°C). Fry the chicken pieces in batches, turning once, until golden brown and cooked through (internal temperature 165°F), about 6-8 minutes per side. Transfer to a wire rack to drain.

Stir together the mayonnaise and Sriracha in a small bowl until smooth. Set aside.

Wash and dry the lettuce leaves. Set pickles and coleslaw nearby.

Slice the burger buns in half. Melt the butter in a skillet over medium heat and toast the cut sides of the buns until golden and fragrant.

Spread about 1 tablespoon of spicy mayo on the bottom half of each bun. Top with a lettuce leaf, a piece of crispy chicken, a few pickle slices, and a generous spoonful of coleslaw.

Spread the remaining spicy mayo on the top half of each bun and place it on top. Serve immediately.