1 tablespoon butter
½ cup diced shallots
1 cup dry red wine
¾ cup ruby Port
1 cup beef stock
1 sprig fresh rosemary or ½ teaspoon dried
Melt butter in heavy large saucepan over medium-high heat. Add shallots and sauté until tender, about 3 minutes. Stir in wine and Port. Boil 5 minutes. Add broth and rosemary sprig and boil until liquid is reduced to ⅓ cup, about 12 minutes. Strain sauce and set aside.
Heat oil in heavy large skillet over medium-high heat. Season steaks with salt and pepper. Add steaks to skillet and cook to desired doneness. Transfer steaks to platter. Add sauce to skillet and bring to boil, scraping up any browned bits. Remove from heat. Gradually add butter, whisking just until melted. Stir in chopped rosemary. Season to taste with salt and pepper.
Spoon sauce over steaks and serve.