Heat the oil in a hot frying pan and sear the steaks for 2 minutes on each side (they will continue cooking in the oven). Remove and set aside.
Brush each sheet of pastry with melted butter and arrange 2 sheets on a work surface. Place a steak in the centre of the pastry, followed by a slice of mozzarella, one-quarter of the herbs and sun-blushed tomato shreds. Season and bring up the sides of the pastry. Scrunch it together at the top to seal the steak into a parcel. Sprinkle over one-quarter of the grated Parmesan. Repeat with the remaining steaks.
Cook in a preheated oven, 220°C (425°F), Gas Mark 7, for 15 minutes until the pastry is crisp and golden brown. Remove and leave to rest for 2–3 minutes.
Toss the salad ingredients together, season and serve with the parcels.