Place the 4 chicken thighs in a bag or bowl, pour over the 1 cup dill pickle juice, and refrigerate for at least 30 minutes. Pat completely dry before proceeding.

Heat the oven to 450°F (230°C). Whisk together the 2 cups flour, 1 tbsp baking powder, 1 tsp salt, and 1 tsp sugar. Work in the 6 tbsp cold butter until shaggy, then stir in the 3/4 cup cold buttermilk until just combined.

Pat the dough to 3/4 inch thick and cut out 4 biscuits with a 3-inch cutter. Place them touching on a baking sheet and bake for 12 to 14 minutes at 450°F (230°C), until tops are golden.

Whisk the 1 cup whole milk with the 1 large egg in one bowl. In another, mix the 1 cup all-purpose flour, 2 tbsp powdered sugar, 1 tsp paprika, 1 tsp salt, 1/2 tsp black pepper, and 1/2 tsp garlic powder. Dredge each chicken piece through the wash then the flour, and rest 5 minutes.

Heat vegetable oil to 350°F (175°C) in a heavy skillet to 2 inches depth. Fry the chicken in batches for 4 to 5 minutes per side until deep golden and 165°F (74°C) internal. Drain on a wire rack.

Split the warm biscuits, place 1 fried chicken thigh on each bottom half, top with 2 to 3 pickle slices, and set the biscuit lid on at an angle. Serve immediately.