Whisk the buttermilk, 2 tablespoons hot sauce, the garlic, thyme, 1/2 teaspoon salt and a few grinds of pepper in a large bowl. Add the chicken and turn to coat. Cover and refrigerate 30 minutes.
Meanwhile, combine the cornflakes, flour, 1/2 teaspoon salt and a few grinds of pepper in a shallow baking dish. Combine the honey and the remaining 2 tablespoons hot sauce in a small bowl; set aside.
Heat 1/2 inch of peanut oil in a large cast-iron skillet over medium-high heat until a deep-fry thermometer registers 350 degrees F. Meanwhile, remove the chicken cutlets from the buttermilk mixture, letting the excess drip off, then press into the cereal mixture on both sides. Working in batches, fry the chicken until golden and crisp, about 2 minutes per side. Transfer to a rack set over a baking sheet and season with salt.
Brush the cut sides of the biscuits with the mayonnaise; sandwich with the fried chicken, lettuce, pickles and a drizzle of the spicy honey.