Reduce port in a saucepan to a syrup consistency, approximately 1/4 to 1/2 cup.

Score the duck breasts on the skin side, taking care not to cut into the meat.

Heat a sauté pan and add the breasts, skinside down. Cook over medium heat 5 to 6 minutes in their own fat until the skin is deep golden brown and crispy. Turn the breast over and finish cooking for about a minute more.

Remove from the pan and let rest for 7 minutes.

Pour off excess fat and add reduced port wine, bring to boil, whisk in butter and vinegar and correct seasoning.

Turn off heat. Thinly slice breasts and divide between 4 warm plates. Coat with sauce.

(Optional) Garnish with small, glazed onions, turnips, sautéed mushrooms, and/or spinach