1. Preheat oven to 190°C. Toss potatoes with oil, salt and pepper on a baking tray and roast for 20-25 minutes until cooked.
2. Meanwhile, place 1 tablespoon oil in a dish with half the garlic. Season, then add the steak and coat in the mixture. Set aside.
3. Place the green beans, red onion and halved cherry tomatoes in a bowl.
4. Mix mayonnaise, vinegar, horseradish, and remaining oil and garlic. Set aside.
5. Heat a chargrill over high heat. When hot, cook steak for 2-3 minutes each side, or until cooked to your liking.
6. Set aside to rest for 5 minutes, then slice thinly and toss with salad ingredients and roast potatoes. Drizzle with the dressing, then sprinkle with parsley.