Brown the meat and onions in a pan. Add the flour and pepper, and cook until the flour starts to brown. Add the Worcestershire, and vegemite and cook until a sauce forms. Cool the filling then put one sheet of puff pastry into a pie pan. Add the cooled meat mixture to the pie pan, and cover with the remainder of the puff pastry. Cover with melted butter or egg wash for a nice crisp coating. Bake at 425 for 15 minutes. Cover with ketchup and enjoy.