Heat a heavy based pan on high.
Brush oil onto both sides of steak.
To seal, cook steak 2-3 minutes each side.
Turn when juices appear on uncooked side note: Steak thickness determines cooking time.
As a gudie: Rare remove after sealing; reduce heat for medium and cook and extra 2-3 minutes each side; Well done, 4-6 minutes each side.
Test steak by pressing with tongs.
Medium has some resistance.
Well done feels quite firm.
Remove from heat, rest while making sauce.
Add onion and mushrooms to any pan juices.
Add worcestershire sauce and stock.
Bring to boil, stirring constantly until slightly thickened.
Add parsley and any juices from rested steak.
Serve with steamed vegetables and mash potatoes.