Season chicken on both sides with salt and pepper. Stir together rice, mango, onion, pistachios, cranberries and spices in a medium foil pan or on a very large piece of heavy duty foil. Place about 1/3 cup of rice mixture in the center of each chicken breast. Bring in the ends and sides to enclose, then tie with kitchen string to seal in filling. Grill over medium-high heat for 5 minutes on each side, then place chicken on top of remaining rice mixture. Cover with foil or seal foil package, leaving room for air to circulate. Grill for 5 minutes more.
If desired, slice chicken into medallions to serve.
Nutritional analysis per serving: Calories 519; Protein 63 g; Carbohydrates 42 g; Fat 11 g; 18% Calories from Fat; Cholesterol 148 mg; Sodium 303 mg; Potassium 1005 mg; Fiber 5 g