Place the chicken thighs in a bowl and pour the buttermilk over them. Turn to coat, cover, and let sit in the fridge for at least 1 hour.

In a large bowl, stir together 2 cups of the flour, 1 teaspoon salt, paprika, garlic powder, and black pepper. Set this mixture aside for the chicken coating.

In a second bowl, whisk the remaining 2 cups flour, baking powder, and remaining 1 teaspoon salt. Cut the cold butter into the dry mix using a fork or pastry cutter until the pieces are pea-sized.

Pour the milk into the biscuit bowl and stir just until a shaggy dough forms. Turn the dough onto a lightly floured surface, pat it into a 1-inch thick rectangle, and cut into 4 squares. Place the squares on a baking sheet.

Heat 2 inches of vegetable oil in a deep skillet or Dutch oven to 350 degrees F. Remove each chicken thigh from the buttermilk, let excess drip off, then dredge in the seasoned flour until fully coated.

Fry the chicken in batches for 12 to 15 minutes, turning once, until the coating is deep golden and the internal temperature reaches 165 degrees F. Drain on a wire rack.

While the chicken rests, bake the biscuits at 425 degrees F for 12 to 15 minutes until the tops are lightly browned.