There are two main reasons the inside of fried chicken stays raw: the oil is too hot, and the pieces are thick. Hot oil darkens the crust within minutes, but heat takes much longer to reach the center near the bone. The solution is to lower the oil temperature or finish cooking the fried pieces in the oven. Doneness is determined not by color but by an internal temperature of 74 °C / 165 °F, measured at the thickest point.
Two separate processes happen at the same time during frying. The surface browns and forms a crust quickly because it is in direct contact with the oil. Heat reaches the center much more slowly, depending on the thickness of the piece. If the oil is above 190 °C / 375 °F, the crust turns dark brown in five or six minutes; yet the middle of a bone-in thigh or a thick piece of breast has only warmed by then. From the outside, the chicken looks browned; inside, it still has an uncooked center.
The thickness of the pieces widens this gap. Bone-in thighs, drumsticks, and whole wings heat the meat around the bone last. A cold piece taken straight from the refrigerator also delays heat reaching the center. Frying thick and thin pieces together in the same pot produces two results at once: the thin pieces dry out while the thick pieces stay raw. For this reason, pieces are sorted by size and each size is fried in its own batch; thick pieces can be cut in half if desired. Wings and drumsticks are also sorted separately; the two do not cook in the same amount of time.
Adjusting the temperature is the first step toward a solution. Fry thick chicken pieces in oil at 160–170 °C / 320–340 °F; at this temperature, the crust colors more slowly, leaving time for the center to heat through. The cooking time increases with the thickness of the piece and can reach fifteen minutes for bone-in pieces. Monitor the oil temperature with a thermometer; after the pieces go in, raise the heat one notch to keep the falling temperature within the range. Add only a small number of pieces to the pot at a time. Do not cover the pot during frying; steam that collects under the lid softens the crust.
The second solution is to finish frying in the oven. If the crust has reached the desired color but the inside is not yet cooked, transfer the pieces to a wire rack and cook them in a preheated 180 °C / 355 °F oven until they reach the required internal temperature. This method also works for a large meal: fry all the pieces first, then finish them together in the oven. The crust does not darken much further in the oven because dry hot air does not brown food as quickly as oil. Arrange the pieces in the oven with space between them, not stacked.
Make the decision by measurement, not color. Insert the thermometer tip into the thickest part of the piece without touching the bone; the internal temperature should be 74 °C / 165 °F. A reading that touches the bone can be misleading because bone conducts heat differently. Clear juices or white meat are not reliable indicators. Measure the thickest piece and, if in doubt, repeat the measurement at a second point. Let the chicken rest for a few minutes after measuring, then serve.