Preheat oven to 200°C (180° fan-forced). Rub beef with oil and sprinkle with paprika. Season. Place beef on a rack over a large roasting tin and cook in oven for 20 minutes.
In a medium bowl combine Worcestershire sauce, tomato paste and stock. Add onions and mushrooms. Season and stir to combine. Remove beef from oven. Reduce heat to 180°C (160° fan-forced). Pour mushroom sauce into base of roasting tin. Return to oven and cook beef for a further 20-25 minutes or until cooked to your liking. Transfer beef to a plate. Cover loosely with foil and set aside to rest for 10 minutes. Add sour cream to mushrooms in pan and stir to combine. Season.
Thinly slice beef. Serve with mushroom sauce, rice, rocket leaves, pickles and parsley.