Melt 1 tablespoon butter in a heavy skillet over medium-high heat; add roast, and brown on all sides. Place in a roasting pan, and cool slightly.
Combine mustard seeds and next 3 ingredients in a heavy-duty zip-top plastic bag; seal. Crush spices with a meat mallet or rolling pin.
Combine crushed spices, 2 tablespoons flour, and next 3 ingredients; stir in 1/4 cup butter and 2 tablespoons Dijon mustard. Spread on top and sides of roast.
Bake at 475° for 20 minutes; reduce heat to 325°. Loosely cover with aluminum foil, and bake 1 hour and 10 minutes or until a meat thermometer inserted in thickest portion registers 160°. Remove roast from pan, reserving 2 tablespoons drippings; keep warm.
Combine reserved drippings, 1 tablespoon flour, 2 tablespoons apple cider, cider vinegar, and 1 teaspoon Dijon mustard; set aside.
Bring remaining apple cider to a boil in a saucepan over medium-high heat; boil 8 minutes or until reduced to 3/4 cup. Stir in brandy; boil 1 minute.
Whisk in flour mixture, salt, and pepper; cook over medium-high heat until thickened. Serve with roast. Garnish, if desired.