Dissolve 2 tablespoons sugar, 1½ tablespoons table salt, 1 tablespoon garlic powder, and ½ teaspoon cayenne pepper in 1 quart cold water in large container.

Add 4 pounds trimmed, bone-in chicken pieces to brine and refrigerate for at least 2 hours or up to 24 hours.

FOR THE DREDGE: Whisk together 2 cups cornstarch, 1 cup all-purpose flour, 4 teaspoons dried thyme, 1 tablespoon garlic powder, 1 tablespoon pepper, 2 teaspoons baking powder, 2 teaspoons onion powder, and ¼ teaspoon cayenne in large bowl until well combined.

Remove 1¼ cups (5 ½ ounces) cornstarch mixture. Transfer remaining mixture to baking pan for dredging chicken.

FOR THE BATTER: Return reserved cornstarch mixture to bowl and whisk in ⅔ cup buttermilk, 1 teaspoon table salt, and 1 teaspoon sugar until smooth batter forms.

Add peanut or vegetable oil to large Dutch oven until it measures 1¾ inches deep. Heat over medium heat to 340 degrees.

Place wire rack in rimmed baking sheet and set aside.

Remove chicken from brine, pat dry with paper towels, and add to batter; toss until evenly coated.

Use 1 hand to lift 1 piece of chicken from batter, allowing excess to drip back into bowl. Place chicken in dredge and cover with dredge until lightly but evenly coated.

Shake to remove excess dredge and add to oil. Repeat until half of chicken has been added to oil.

Fry chicken, adjusting burner if necessary to maintain oil temperature between 305 and 315 degrees, until breasts register 145 degrees and drumsticks/thighs register 160 degrees, 10 to 18 minutes. Transfer chicken to prepared rack.

Return oil to 340 degrees and repeat with remaining chicken.

Let chicken rest for 20 minutes before serving.