MAKES 4 SERVINGS
2 cups buttermilk
1⁄4 cup Dijon mustard
2 tablespoons onion powder (with green onion and parsley)
5 teaspoons salt
4 teaspoons dry mustard
4 teaspoons cayenne pepper
2 1⁄2 teaspoons ground black pepper
1 (3- to 3 1⁄4-pound) chicken, backbone removed, chicken cut into 8 pieces, skinned (except wings)
3 cups all-purpose flour
1 tablespoon baking powder
1 tablespoon garlic powder
5 cups peanut oil, for frying
Special equipment: Deep-fry thermometer
 In a 1-gallon resealable plastic bag, mix the buttermilk, mustard, 1 tablespoon onion powder, 1 teaspoon salt, 1 tea- spoon dry mustard, 1 teaspoon cayenne, and 1 teaspoon pepper. Add the chicken pieces. Seal the bag, eliminating air. Turn the bag to coat the chicken evenly. Refrigerate at least 1 day and up to 2 days, turning bag occasionally.
 Whisk the flour, baking powder, garlic powder, remaining 1 tablespoon onion powder, 4 teaspoons salt, 3 teaspoons dry mustard, 3 teaspoons cayenne, and 11⁄2 teaspoons pepper in a 13 by 9-inch glass dish. With marinade still clinging to the chicken pieces (do not shake off excess), add the chicken to the flour mixture, turning to coat thickly. Let the chicken stand in the flour mixture for 1 hour, turning chicken occasionally to recoat with flour mixture.
 Pour the oil to a depth of 11⁄4 inches into a 10- to 11-inch pot. Attach a deep-fry thermometer. Heat the oil over medium-high heat to 350°F. Add 4 pieces of chicken, skin side down. Reduce the heat to medium-low and fry 5 minutes, adjusting heat to maintain oil temperature between 280° and 300°F (oil should bubble constantly around chicken). Using wooden spoons, turn the chicken over. Fry 7 minutes. Turn the chicken over again. Fry until deep golden brown and cooked through, about 3 minutes longer. Using the same spoons, transfer the chicken to a large rack set on a baking sheet.
 Reheat the oil to 350°F. Repeat frying with the remain- ing 4 pieces of chicken. Serve the chicken warm or at room temperature within 2 hours, or chill up to 1 day and serve cold.