In a small bowl, mix plums, onion, rice, mushrooms, ginger, and 1 tablespoon soy sauce to make stuffing. Fill hens with stuffing. Baste hens with a mixture of 1 tablespoon olive oil and 1 tablespoon soy sauce. Cook hens for 20 minutes in an oven preheated to 450°F. Reduce heat to 350°F and continue cooking 20 to 30 minutes more, until hens are browned and a meat thermometer registers 185°F. Split hens, remove skin, and arrange with stuffing on 4 plates. Use pan juices as gravy.
Each serving contains about 247 calories, 27 g protein, 8 g fat (30% calories from fat), 117 mg cholesterol, 14 g carbohydrates, 6 g fiber, and 321 mg sodium.