Season the steaks generously with salt and pepper, then rub with a little oil.

Heat a dry frying pan over high heat (add a small amount of oil if necessary).

Sear the steaks for 2-3 minutes on each side, or until browned to your liking.

Add the butter and rosemary to the pan, spoon the melted butter over the steaks, then remove them from the heat.

Let the steaks rest on a plate, covered loosely with foil, while you prepare the gratin.

Heat a large pan over medium heat and add a splash of oil.

Sauté the onion and garlic until softened and fragrant, about 3-4 minutes.

Add the sliced potatoes to the pan and fry for 5-6 minutes, stirring occasionally, until some slices are turning translucent.

Pour in the water and crumble in the stock cube, stirring to combine.

Add the cream and cook for another 2-3 minutes, allowing the sauce to thicken slightly.

Preheat your oven to 200°C (180°C fan)/Gas Mark 6.

Transfer the potato mixture to a baking dish, spreading it out evenly.

Pour over any remaining sauce from the pan.

Place the dish in the oven and bake for 25-30 minutes, or until the potatoes are tender and golden on top.

Slice the rested steak and serve alongside the potato gratin, spooning any resting juices over the meat for extra flavour.