In a large bowl, whisk together 1 1/2 cups buttermilk, the beaten egg, 1 teaspoon kosher salt, paprika, garlic powder, and black pepper. Add the chicken thighs and turn to coat. Cover and refrigerate for at least 1 hour, or up to 8 hours. The chicken should be fully coated and submerged as much as possible.

Heat the oven to 425°F (220°C). Line a baking sheet with parchment paper. In a large bowl, whisk together the flour, baking powder, baking soda, salt, and sugar. Add the cold cubed butter and cut it into the flour with a pastry cutter or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.

Pour in the cold buttermilk and gently stir just until a shaggy dough forms. Do not overmix. Turn the dough onto a lightly floured surface and gently pat it into a rectangle about 3/4 inch (2 cm) thick. Fold it in half once, then pat it back to about 3/4 inch thick. Cut 8 biscuits with a 2 1/2-inch (6-cm) round cutter, pressing straight down rather than twisting.

Arrange the biscuits close together on the prepared baking sheet. Bake for 14–17 minutes, until the tops are lightly golden and the centers are fully set. Brush the hot biscuits with the 2 tablespoons melted butter. Set aside while you fry the chicken.

In a shallow bowl, whisk together the flour, cornstarch, paprika, garlic powder, onion powder, kosher salt, black pepper, cayenne if using, and baking powder. Drizzle the 1/2 cup buttermilk over the flour mixture and gently toss with your fingers until small, irregular clumps form. These clumps create a craggy fried crust.

Remove the chicken from the marinade, allowing excess buttermilk to drip off. Press each piece firmly into the seasoned flour mixture, turning and pressing so the coating sticks to every surface. Place the coated chicken on a wire rack and let it stand for 5–10 minutes. The coating should look slightly damp and textured rather than powdery.

Pour the oil into a 9-inch cast-iron or heavy-bottomed skillet, filling it to about 1 1/2 inches deep. Heat over medium-high heat to 350°F (175°C). Use a thermometer to monitor the temperature because adding chicken will lower the oil temperature.

Carefully add the chicken in batches, leaving enough room between pieces for the oil to circulate. Fry for about 4–6 minutes per side, depending on thickness, until deeply golden brown and the chicken reaches an internal temperature of 165°F (74°C). Keep the oil around 325–350°F (165–175°C) while frying. Transfer the chicken to a wire rack set over a baking sheet so excess oil can drain without making the crust soggy.

While the chicken rests, combine the honey, hot sauce, crushed red pepper flakes, and butter in a small saucepan. Warm over low heat for 1–2 minutes, stirring until the butter melts and the mixture is smooth. Do not boil the honey. Taste and add more hot sauce only if you want additional heat.

Split each warm biscuit horizontally: Place one piece of fried chicken inside each biscuit and drizzle generously with the warm hot honey. Add optional pickle chips and chopped chives. Serve immediately while the chicken is crisp and the biscuits are warm.