Add first 4 ingredients to a saucepan and bring to a boil over medium-high heat. Reduce heat to medium-low and simmer for 10 minutes. Add cranberries and simmer until cranberries soften. Season sauce with salt and pepper to taste. Adjust flavor to suit your own taste. If the sauce is too tart, stir in a little sugar. Too sweet, a little more vinegar. You get the idea.
Season the duck breasts liberally with salt and pepper. Heat olive oil over medium-high heat in a large skillet. Add duck breasts and sear on one side, about 3 to 4 minutes. Flip over brown other side until breasts are rare to medium-rare. Remove breasts from skillet and let stand for 2 to 3 minutes.