Preheat oven to 350°F. Using long slender knife, carve out 3/4-inch-diameter horizontal tunnel through center of pork. Chop carved-out meat and reserve. Using handle of wooden spoon, firmly pack apricots and prunes into tunnel of roast. Place roast on rack in roasting pan; rub with 1 tablespoon oil. Sprinkle roast with 1/2 teaspoon marjoram, salt, and pepper. Scatter onion, carrots, garlic cloves, and chopped meat around rack in pan. Drizzle vegetables with 1 tablespoon oil; sprinkle with 1 teaspoon marjoram. Roast pork until instant-read thermometer inserted into thickest part of meat (not stuffing) registers 150°F, stirring vegetables occasionally, about 1 hour 25 minutes. Transfer pork to cutting board; tent with foil to keep warm.
Whisk butter, flour, and both mustards in small bowl to blend. Add broth and wine to roasting pan; place on 2 burners and simmer juices over medium heat until mixture is reduced to 1 1/2 cups, scraping up browned bits, about 3 minutes. Strain liquid into small saucepan; skim fat from surface. Bring liquid to boil. Whisk in mustard mixture; simmer until sauce thickens slightly, whisking frequently, about 3 minutes. Season with salt and pepper.
Cut pork between ribs into chops. Serve with sauce.
What to drink: Prinz von Hessen 2001 Riesling Kabinett Winkeler Hasensprung.