Meanwhile put the shallots in a large frying pan, add the sugar and balsamic and cook, turning, until caramelised. To make the gravy, drain all but 1 tbsp fat from the roasting tin and put the tin over a medium heat. Add the plain flour and cook for about 1 minute stirring constantly. Add the red wine and reduce by half, stirring to remove any caramelised bits from the bottom of the pan. Add the beef stock and continue to simmer until the gravy has thickened slightly. Season and pour into a jug to serve alongside the beef.