In a medium sized bowl, mix together hot sauce and buttermilk until combined. Set aside.
In a separate bowl, whisk together flour, cornstarch, seasoned salt, cayenne, paprika, garlic powder, and onion powder until combined.
Dip each piece of chicken into the seasoned flour, then back into the buttermilk, and then back into the seasoned flour again. Be sure that each piece is evenly coated. Set pieces onto a baking sheet while your oil heats.
Add 2 - 2½ inches of oil to a large cast iron skillet or heavy bottom skillet. Heat oil over medium high heat. Heat oven to 275 degrees.
Oil is ready when a thermometer reads 350 degrees. Carefully place in 2 - 3 pieces of chicken so they aren't crowded. Fry 7 - 8 minutes until golden brown, flipping halfway through.
Remove chicken from oil and place on a clean rack. Put in oven to keep warm and crisp.
Use a ladle to scoop ¾ cup of fry oil from the pot into a heat-proof mixing bowl. Then mix in cayenne, dark brown sugar, chili powder, and garlic powder.
Remove chicken from the oven and brus hot oil on all sides. Place a piece of chicken on the bun and top with pickles and lettuce.