Rub the steak with the oil and season with salt and freshly ground black pepper on both sides.
Heat a frying pan until smoking. Add the beef and fry for two minutes on each side.
Add the balsamic vinegar and reduce by half.
Add the honey and cook for a further minute. Remove the beef rest for 2-3 minutes and then slice.
For the potatoes, heat the olive oil in an ovenproof frying pan. Add the potato slices and fry for two minutes on each side, until crisp and golden. Season with salt and freshly ground black pepper and transfer to the oven to roast for five minutes.
For the rosemary oil, gently heat the olive oil and rosemary in a frying pan for 1-2 minutes, then remove from the heat and leave to infuse for five minutes.
For the spinach, melt the butter with the olive oil in a large pan, then add the spinach. Cook until the spinach has wilted down, then season, to taste, with salt and freshly ground black pepper. Squeeze out the excess moisture and place onto a plate.
Serve the sliced beef with the spinach and drizzle the pan juices over the top. Arrange the potatoes alongside and spoon over some of the rosemary oil.