This recipe made its debut at a ballpark stand at Citizens Bank Park, home of the Philadelphia Phillies. Roasting the BBQ blend on a baking sheet blooms the spices and caramelizes the sugar, creating the perfect deep-flavored dusting to settle into the crunchy crevices of hot fried chicken (or potato chips!).
BBQ Spice Blend: Preheat oven to 350 F. In a mixing bowl, combine onion powder, black pepper, chili powder, smoked paprika, thyme, salt, brown sugar, and sumac. Spread the spice mixture evenly in a baking pan and bake until the mixture is fragrant, about 10 minutes. Remove from the oven and let cool, about 10 minutes. Pulse in a food processor until finely ground. Pour onto parchment paper, then pull up the edges to create a funnel. Gently pour the spice mixture into a shaker or lidded container. Set aside. Makes about 1 cup. (Store in an airtight container at room temperature.)
Cure chicken: In a large bowl, add salt and mustard and onion powders, and combine until well blended. Add the chicken pieces and get in there with your hands to coat each piece well. On a baking sheet lined with parchment paper, arrange the coated chicken pieces in a single layer, keeping the skin intact; lightly cover with parchment paper or plastic wrap. Refrigerate for at least 4 hours or up to overnight.
Bring the cured chicken to room temperature. (You don’t want to fry ice-cold chicken, because it won’t cook all the way through, and it will chill the frying oil.) Meanwhile, make the batter: In a large bowl, add the cornstarch, flour, and salt. Slowly pour in the cold water, whisking continuously, until the mixture is smooth and the consistency of thin pancake batter. Add more water as needed to thin the batter.
Heat oil: Clip a candy or deep fry thermometer onto a large, heavy pot. Add enough canola oil to fully submerge the chicken pieces—about halfway up the side of the pot. (Oil expands as it heats, so don’t overfill the pot.) Heat the oil over low heat until it reaches 300 F. (It’s fine if the oil temperature goes up to 350 F, because it will drop once the chicken goes in.) Coat chicken: When the oil is hot, add all the chicken into the batter and fully coat each piece.
First fry: Starting with the dark meat, use tongs to pick up each piece and allow the excess batter to drip off. Gently swirl the tip of the chicken in the oil to set the crust; this will prevent the chicken from sticking to the bottom of the pot. Then ease the rest of the piece into the oil. Repeat with all the chicken pieces. Use a slotted spoon or spider strainer to make sure the chicken pieces don’t stick together or to the bottom of the pot. If they do stick, gently separate them with the spoon; try not to tear the delicate crust!
After 10 minutes total, use the slotted spoon to transfer the chicken pieces to drain on a wire rack or paper towels on a baking sheet. The chicken will not be fully cooked—there’s a second fry. Let the chicken rest, 15–20 minutes. Meanwhile, reheat the oil to 350 F. (Note: The chicken can be made to this point up to 1 day ahead and refrigerated; bring it back to room temperature before the second fry.) Second fry: When the oil is hot, fry the chicken pieces again, this time for 4 minutes or until golden brown and crispy.
Use the slotted spoon to transfer the chicken pieces to drain on a clean wire rack set over a paper towel-lined baking sheet. Sprinkle BBQ Spice Blend on all sides of the chicken from a spice shaker, or sprinkle it on the chicken with your fingers. Reserve any spice blend on the bottom of the tray to reuse on more chicken. Serve immediately.
Frying oil can be reused several times for frying chicken. Cool the oil completely, then pour through a fine-mesh strainer into a clean jar. Cover and store in the refrigerator for up to two weeks.