3 tablespoons butter
3 tablespoons sugar
1/3 cup dry white wine
1/3 cup orange juice
2 tablespoons raspberry vinegar
1 1/4 cups frozen blackberries, thawed
1 1/4 cups canned beef broth
1/2 cup canned low-salt chicken broth
2 tablespoons Cognac or brandy
1 tablespoon pure maple syrup
4 5- to 6-ounce duck breast halves with skin
Melt 2 tablespoons butter in heavy large nonstick skillet over medium-high heat. Add sugar; stir until sugar dissolves and mixture turns deep amber color, about 5 minutes. Add wine, orange juice and vinegar (mixture will bubble vigorously) and bring to boil, stirring to dissolve caramel. Add 1 1/4 cups berries and both broths and boil until sauce thickens and is reduced to about 1 cup, stirring occasionally, about 25 minutes. Strain sauce through sieve into heavy small saucepan, pressing on berries with back of spoon. Mix in Cognac and maple syrup. Set sauce aside. (Can be prepared 1 day ahead. Cover and chill.)
Preheat oven to 400°F. Trim any excess fat from duck breasts. Cut three 4-inch-long by 1/16-inch-deep lengthwise slits in skin (not meat) of duck. Season duck with salt and pepper. Heat heavy large ovenproof skillet over high heat until hot. Add duck, skin side down, and sear until brown, about 5 minutes. Turn over; cook 3 minutes. Transfer skillet to oven; continue cooking to desired doneness, about 3 minutes for medium.
Meanwhile, bring sauce to simmer over low heat. Add remaining 1 tablespoon butter and whisk just until melted. Season to taste with salt and pepper.
Spoon sauce onto plates. Slice duck and place atop sauce. Garnish with additional berries, if desired, and serve.