Brine the Chicken
In a large bowl, whisk together the buttermilk, hot sauce, onion powder, garlic powder, smoked paprika, salt, black pepper, and chili powder. Add the chicken thighs, cover, and refrigerate for at least 2 hours or up to 24 hours.
Prepare the Dredge
In another bowl, mix flour, cornstarch, baking powder, salt, rosemary, paprika, garlic powder, and optional honey. Add a few teaspoons of the brine into the mixture to create texture.
Coat the Chicken
Remove chicken from the brine and coat thoroughly in the flour mixture. Press gently and shake off excess.
Fry the Chicken
Heat oil to 350°F (175°C). Fry chicken in batches for 7–8 minutes until golden brown and cooked through (internal temp 165°F). Set aside on a rack.
Make the Biscuits
Preheat oven to 425°F (220°C). Mix flour, baking powder, baking soda, and salt. Add grated butter and combine.
Stir in honey and buttermilk until a shaggy dough forms. Fold and flatten the dough several times to create layers. Roll to 1-inch thickness and cut biscuits.
Brush tops with melted butter and honey mixture. Bake for 13–15 minutes until golden.
Assemble the Honey Butter Chicken Biscuit
Split a warm biscuit and place a crispy chicken thigh inside. Drizzle with honey butter and serve immediately.