Preheat oven to 475�F. Tie the roaast up neatly at 1 cm intervals with kitchen cord so that it will hold it's shape while cooking. With a pastry brush, spread the softened butter evenly over the meat. Place the roast on a rack in a shallow open roasting pan and sear it in the hot oven for about 20 minutes. When the surface of the meat is quite brown, reduce the heat to 375�F and sprinkle the roast generously with salt and pepper. Pour the stock into the pan and cook the roast, uncovered, for 1.25 hours. With a large spoon or bulb baster, baste the meat with the pan juices every half hour or so. The interior meat, when finished, should be slightly rare, or about 150�F on a meat thermometer. Remove the roast to a heated platter, cover it loosely and let rest in the turned off oven while you make the sauce. Skim and discard the fat from the pan juices. Measure the remaining liquid and either reduce to 1 cup by boiling it rapidly or add enough water to make up 1 cup. In a small, heavy saucepan, heat 1 tablespoon of butter and stir in 1 tablespoon of flour. Stirring continuously with a wooden spoon, cook this roux for 6 to 8 minutes over low heat until it is a nut brown color. Be careful not to let it burn or it will give the sauce a bitter flavor. Now, with a wire whisk, beat the pan juices into the roux. Next whisk in the jelly and cheese. Beat until they dissolve and the sauce is absolutely smooth, then stir in the sour cream. Do not allow the sauce to boil. Taste for seasoning, remove the strings from the roast and carve the meat in thin slices. Pass the sauce separately.