4 Portobello mushrooms, brushed clean and cut into thick slices
12 whole cherry tomatoes on the vine
Sea salt and freshly ground black pepper
Watercress, to serve
Mix together the parsley, oregano, garlic, rosemary, chilli, red wine vinegar and a third of the oil. Season with a little salt and pepper then leave to infuse for approximately 2 hours.
When ready to cook, heat a large griddle pan over a high heat.
Brush the steak on both sides with the remaining oil, then, when the griddle is smoking hot, carefully put it on to the pan and fry for 4 minutes on each side. Remove the steak, wrap in tin foil and leave to rest.
Put the sliced mushrooms on to the griddle in a single layer and cook for 2 minutes on each side. Take the mushrooms off the griddle, then add the tomatoes and cook for approximately 2 minutes as well.
Carve the steak against the grain into long, thin slices and arrange the slices on a serving platter. Drizzle with a generous amount of chimichurri sauce and serve with the mushrooms, tomatoes and watercress.