Instructions

1. Preheat oven to 350°F.
2. Pat pork dry and season generously with salt and pepper.
3. Sprinkle center of a flameproof roasting pan with 1/2 tablespoon flour.
4. Set pork on flour in pan and roast in middle of oven 40 minutes.
5. Brush pork with some maple syrup and roast, brushing with maple syrup every 10 minutes, until a thermometer inserted 2 inches into center of meat registers 155°F, 20 to 25 minutes more.
6. While pork is roasting, peel potatoes and cut into 1 1/2-inch pieces.
7. In a kettle cover potatoes with salted cold water by 2 inches and simmer until tender, about 15 minutes.
8. Drain potatoes in a colander set over a large bowl and reserve 3 cups cooking water.
9. Return potatoes to kettle and mash with a potato masher, or purée in a food processor.
10. Season potatoes with salt and pepper and keep warm.
11. Transfer pork to a platter and let stand, loosely covered with foil, 10 minutes.
12. While pork is standing, skim fat from pan juices.
13. In a small bowl make a beurre manié by kneading together butter and remaining 4 tablespoons flour until smooth.
14. Add 1 cup reserved cooking water to roasting pan and deglaze over moderately high heat, stirring and scraping up brown bits.
15. Add remaining 2 cups cooking water and any juices that have accumulated on platter and bring mixture to a boil.
16. Whisk in beurre manié and simmer sauce, whisking, until thickened to desired consistency, about 2 minutes.
17. Pour sauce through a fine sieve into a sauceboat.
18. Slice pork and serve with sweet potatoes and sauce.
19. Serves 6 to 8.