2 tbs olive oil 400g cup mushrooms, diced 1 garlic clove, crushed 1 tbs Worcestershire sauce 1 cup salt-reduced beef stock 1 tsp Dijon mustard 2 tsp cornflour 1 tbs cold tap water 2 tbs chopped flat-leaf parsley 4 beef fillet steaks, trimmed mashed potato & steamed vegetables, to serve