To prepare the cauliflower purée; cook the cauliflower in a large pan of boiling water with the crumbed vegetable stock cube for 15 minutes, or until tender.
Transfer to a food processor or blender, add the melted garlic butter and purée for 1-2 minutes, or until the mixture is smooth. Season if required.
For the mushroom sauce; melt the remaining butter in a non-stick medium frying pan over a moderate heat and gently cook mushrooms for 2-3 minutes, stirring occasionally. Add the sherry and cook for 3-4 minutes or until the sauce is reduced and syrupy.
Heat a non-stick griddle pan over a moderate heat.
Put the steaks on a clean chopping board, season and brush with the oil on both sides.
Cook the steaks according to your preference; transfer to a warm plate and set aside to rest for a few minutes.
Reheat the purée, if required and place the steaks on top, spoon over the mushroom sauce, garnish with the parsley, if used and serve with seasonal vegetables.
Follow the cooking times below:
Based on a 2cm/¾in thick steak:
Rare: 2½ minutes on each side
Medium: 4 minutes on each side
Well done: 6 minutes on each side
For flat iron steaks cook for:
Rare -2 minutes on each side
Medium Rare - 3-4 minutes on each side
Medium -5-7 minutes on each side
For best results with flat iron cover with foil and rest for 5-10 minutes before serving.