2. Brown sesame seeds in butter about 1 min over medium heat.
3. Add coffee, soy sauce, Worcestershire sauce, and vinegar. Heat to boiling.
4. Pour hot marinade over roast. Marinate 8 hours or overnight, covered.
5. Remove roast from marinade. Brown on all sides over medium high heat. Heat marinade to boiling. Place roast in roasting pan with lid, pour marinade over and cover. Bake at 325 deg F for 2 to 2 1/2 hours. May also be placed in a crock pot and cooked on low for 8 to 10 hours or on high for 4 to 5 hours.
6. Remove roast from baking dish. Strain drippings. Skim off excess fat. Bring to a boil.
7. Mix cornstarch with sherry or water. Add slowly while stirring to drippings, whisk until thickened. Stir in sesame seeds, if desired. Pour some over roast, place remainder in dish for serving with meat. Slice to serve.