Make the marinade and divide it into two bowls. Add the cabbage stems to one bowl and the chicken to another (you could marinate the meat and vegetables together, but this way is safer). Leave in the fridge for 3-4 hours, covered.
About an hour before serving, preheat the oven to 325 F. Transfer the stems, with the marinade, to a baking dish. Add the orange slices and the stems and oranges while you prepare the chicken.
Set up two plates. On one plate, add the egg and cornstarch and whisk to combine. On the second plate add the panko.
Remove the chicken chunks from the marinade and discard the marinade. Heat half the oil in a large frying pan; fry half the chicken chunks on one side, about 5 minutes until they are golden brown, then flip them and fry the other side for 3 minutes. Cut one chunk to make sure it is cooked through; if not, fry a bit longer. Transfer to a plate, add the rest of the oil to the pan, and fry the rest of the chunks.
Carefully remove the baking dish from the oven, add the chicken and stir gently to coat the chicken with the marinade. If the marinade has reduced to the point where it can’t be ladled, add more orange and water. Sprinkle the peanuts on top. Bake for 25 minutes, basting after 10 minutes and adding more orange juice or water if the sauce becomes too thick. Remove from oven and serve hot.