1 Heat the oven to 220°C (200° fan) 425°F gas 7.
2 Heat the oil in a pan. Season the meat with salt and pepper and brown the meat quickly on all sides.
3 Put into a roasting tin and cook in the oven for 20 minutes for medium rare, or until cooked to your liking. Remove from the oven, cover with foil and leave to rest while you make the sauce.
4 For the sauce: pour the meat juices into a shallow pan. Add the oil, water and vinegar and bring to a boil. Simmer for 1-2 minutes until thickened. Add the chocolate and stir until melted.
5 For the asparagus: put the asparagus into a frying pan and add just enough boiling water to cover. Add the salt and cook for 4-8 minutes until tender, but not soft - the actual time depends on the thickness of the stems. Drain very well.
6 Slice the meat and place on warm serving plates. Drizzle over the chocolate sauce and place the asparagus spears on each plate.