1. Prepare the marinade: lightly toast the spices in a dry pan for 3 or 4 minutes or until they become fragrant. Crush the spice mix in a mortar and pestle.
2. Rub the steaks with the spices and oil and leave to sit for at least 40 minutes.
4. In a lined roasting dish place the beetroot, mushrooms, thyme, shallots and garlic. Add the cumin, brown sugar and olive oil and massage into the vegetables.
5. Place in the oven for 40-50 minutes until the beetroot has softened, stirring once or twice while cooking. Remove from the oven, toss over the balsamic and allow to cool slightly.
6. Preheat a barbecue to a medium heat. Place the steak on the grill for 4 or 5 minutes before turning and repeating on the other side. Let it rest for 5 minutes.
7. Toss the olive and watercress through the beetroot and serve with the steak.