Roast Pork Loin in Beer Sauce

Ingredients

 * 3½-pound boneless pork loin, tied (3 to 3½ inches wide)
 * 2 tablespoons olive oil

Beurre manié

 * 1 tablespoon softened unsalted butter
 * 1 tablespoon all-purpose flour

Marinade

 * ½ cup Dijon mustard
 * 1 large onion, chopped
 * ½ cup honey
 * 3 cups beer (not dark), preferably German

Marinade

 * 1) In a large saucepan, stir together marinade ingredients.
 * 2) Bring marinade just to a boil, stirring (marinade will rise and foam), and remove pan from heat.
 * 3) In a blender, purée marinade in 2 batches, transferring it as puréed to bowl.
 * 4) Cool the marinade to room temperature and spoon off any remaining foam.

Beurre manié

 * 1) Mix by rubbing together softened butter and 1 flour.

Assembly

 * 1) In a large heavy resealable plastic bag combine pork and marinade and seal bag, pressing out any excess air.
 * 2) Put the bag in a baking pan and marinate pork, chilled, turning bag once or twice, at least 8 hours and up to 24.
 * 3) Let pork in marinade come to room temperature, about 40 minutes.
 * 4) Transfer marinade to a saucepan and bring just to a boil.
 * 5) Preheat oven to 375°F.
 * 6) Pat pork dry with paper towels and season with salt and pepper.
 * 7) In a flameproof roasting pan, heat oil over moderately high heat until hot but not smoking and brown pork on all sides.
 * 8) Roast pork in the middle of the oven, basting frequently with some marinade, until a meat thermometer registers 155°F (for slightly pink meat, cook 1 to 1½ hours).
 * 9) Transfer pork to a cutting board, reserving juices in roasting pan and discarding string, and let stand, covered loosely with foil, about 15 minutes.
 * 10) While pork is standing, skim and discard fat from pan and add remaining marinade.
 * 11) Deglaze the roasting pan over moderately high heat, scraping up brown bits.
 * 12) Bring the sauce just to a boil and strain through a fine sieve into another saucepan.
 * 13) Bring the sauce to a simmer and whisk in beurre manié, bit by bit, whisking until sauce is combined well and thickened slightly.
 * 14) Serve pork, sliced, with sauce.