Method:
1 Preheat oven 200°C fan-forced. 
2 Heat oil in a frying pan over medium heat. Season steak with salt and pepper and cook for 3 minutes each side for medium rare or until cooked to your liking. Rest for 3 minutes.
3 Combine fennel, lemon juice, onion and chives in a bowl.  Add mayonnaise and season with salt and pepper. Toss to combine.
4 Heat butter and a little oil in a frying pan over medium heat add mushrooms, thyme and rosemary and cook for 2-3 minutes then transfer to the oven and roast for 4-5 minutes or until mushrooms are light golden and tender. 
5 Place the steak on a serving plate, top with king brown mushrooms and serve with fennel slaw.