Preheat the oven to 190°C. Mash the garlic with the pepper using the side of a chef's knife, to form a chunky paste. Rub this on to both sides of the steak. Set aside.
Put the potatoes in a saucepan of water and bring to the boil. Reduce the heat and simmer for 5 minutes. Add the beans and cook for a further 3–4 minutes or until the potatoes are tender and the beans are al dente. Drain, rinse with cool water and transfer to a large bowl.
Put the onion in a colander and rinse with hot water. Mix together the vinegar, oil, sugar, salt and pepper in a small bowl. Set this vinaigrette aside.
Heat a large, heavy ovenproof frying pan over medium-high heat until very hot but not smoking. Add the steak and sear for about 3 minutes on each side or until browned. Transfer to the oven. For medium-rare steak, cook for 15–18 minutes; for medium cook for 20–23 minutes. Leave to rest for 5 minutes, then trim off any remaining fat and thinly slice the steak. To serve, arrange the potatoes, beans and onions around the steak on a platter and drizzle with the vinaigrette.
Some more ideas
*For a tasty change, roast the potatoes instead of boiling them. *Use 450g cubed sweet potatoes in place of the new potatoes. *Replace the green beans with sweet peas. *For a mellow flavour, toss the red onion in balsamic vinegar instead of white wine vinegar.
*A 125g serving of beef (which is what you get in this recipe) provides a whopping supply of vitamin B12. It is also an excellent source of iron and zinc. *The red onion in this dish is particularly healthy for your cardiovascular system. In addition to being high in fibre, it offers large amounts of antioxidants, particularly quercetin, a potent flavonoid linked to a reduced risk of cancer, cardiovascular disease and cataracts.