Grilled Duck Breasts with Orange Balsamic Glaze

cups orange juice
1/2 cup balsamic vinegar
1 whole (1¾ pound) boneless duck breast, trimmed of all skin and visible fat, and separated into 4 equal pieces
2 small shallots, finely chopped
1/2 cup dry red wine or reduced sodium chicken broth
1 tablespoon grated orange zest
1/4 teaspoon salt
1/8 teaspoon ground white pepper
1 bunch arugula, torn into bite-size pieces (optional)

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