Roast Pork Loin with Beer Sauce

In a large saucepan stir together marinade ingredients. Bring marinade just to a boil, stirring. The marinade will rise and foam. Remove the pan from the heat. In a blender, puree marinade in 2 batches, transferring it as it is pureed to a bowl. Cool marinade to room temperature and spoon off any remaining foam. In a large resealable heavy plastic bag, combine pork and marinade and seal bag, pressing out any excess air. Put bag in a roasting bag and marinate pork, chilled, turning bag once or twice, at least 8 hours and up to 24. Let pork and marinade come to room temperature, about 40 minutes. Transfer marinade to a saucepan and bring just to a boil. Preheat oven to 350 degrees. Pat pork dry with paper towels and season with salt and pepper. In a flame proof roasting pan heat oil over moderately high heat until hot but not smoking. Brown pork on all sides. Roast pork in the middle of the oven, basting frequently with the marinade until a meat thermometer registers 155 degrees, about 1 to 1 and 1/2 hours. Transfer pork to cutting board, discard string and cover loosely with foil for about 15 minutes. Skim and discard fat from pan and add remaining marinade. Deglaze pan. Bring marinade just to a boil and strain through a fine sieve into another saucepan. Bring sauce to a simmer. Make the beurre mannie by rubbing together the butter and flour. Whisk the beurre mannie, bit by bit, into the sauce until it is combined well and slightly thickened. Serves 6.