The website CopyCatRecipeGuide.com offers a recipe for replicating Panda Express' famous Mandarin chicken. The recipe requires only two ingredients: boneless chicken thigh (or other dark meat) and Panda Express Mandarin sauce.
Start by cleaning and preparing one pound of the boneless chicken thigh or dark meat of choice. Place the chicken in a medium-sized bowl, and pour over it half a cup of the Panda Express Mandarin sauce, and then stir to ensure all pieces of chicken are covered. Next, to marinate, cover the bowl and refrigerate the container of chicken for about 30 minutes.
Preheat the grilling surface, and remove the chicken from the refrigerator. Using tongs, place the pieces of chicken upon the grill, making sure to grill each side. To ensure thorough cooking, the internal temperature of the chicken should be at least 165 F. Remove the chicken once it is done, cut it into strips, and place it in a bowl. Heat half a cup of the Mandarin sauce, and pour the sauce over the grilled chicken. Stir once more to evenly coat.