- Preheat the oven to 200°C, 180°C Fan, Gas Mark 6.
- Heat half the oil in a large non-stick frying pan and fry the onions, garlic and thyme leaves for 5 minutes until soft.
- Place a layer of potatoes in a 1½ litre dish. Scatter over some of the onion mixture and continue to layer the potatoes and onions until you finish with a layer of potatoes.
- Pour over the stock and transfer to the oven and roast for 20 minutes until golden. Cover with foil and cook for a further 40 minutes until the potatoes are tender.
- Towards the end of the cooking time, heat the remaining oil in a large non-stick pan or griddle pan over a medium to high heat. Cook the steaks for 2 minutes on each side for a rare, 3 minutes for medium and 4 minutes for well done. Remove from the pan, cover loosely with foil and leave to rest for 5 minutes.
- Place the green beans in a pan of boiling water and cook for 2-3 minutes until just tender. Drain and serve with the steak and potatoes.