Cornish Game Hens with Sweet-Potato Risotto and Cranberry Sauce

1 cup water

1 cup cranberries

1/4 cup ruby Port

2 Cornish game hen s, halved lengthwise

2 tablespoons (1/4 stick) butter

1 pound yams (red-skinned sweet potato es), peeled, cut into 1/2-inch pieces

1 onion , chopped

1/4 teaspoon minced peeled fresh ginger

2/3 cup arborio rice or medium-grain rice

1/4 cup dry Riesling wine

2/3 cup mascarpone cheese*

1/4 cup walnut s, toasted, chopped

1/4 cup chopped fresh parsley

1 teaspoon grated orange peel