Ingredients

Step by step

1. Place a baking tray in the oven and preheat to 220°C, fan 200°C, gas 7. Parboil the potatoes for 5 minutes, then drain and toss with 2 teaspoons of the oil and the mustard. Season well, spread out on the hot baking tray and roast for 18-20 minutes.
2. Trim the fat from the steak, rub the steak with 1 teaspoon of the oil, season and set aside. Once the potatoes have had 5 minutes in the oven, heat a dry frying pan on a high heat, add the steak and cook for 2-3 minutes each side, or to your liking. Set aside to rest on a warm plate, loosely covered with foil.
3. Return the pan to a low heat, add the butter and anchovies. Stir to melt and heat through, scraping up any crispy bits from the base of the pan. Keep warm over a very low heat.
4. Once cooked and crispy, tip the hot potatoes into a bowl with the watercress; toss to combine.
5. Add the resting juices from the steak to the anchovy butter, along with the chopped parsley. Stir a little of this through the bowl of watercress and potatoes.
6. Thinly slice the steak and divide between two plates. Drizzle with the rest of the anchovy and parsley butter and serve alongside the watercress and roasted potatoes.