Seared Sirloin with Triple-Cooked-Style Chips and Thyme Mushroom Sauce

Heat the tray and oven

Heat the oven to 220°C/200°C fan/gas 7. Put a large baking tray in the oven to heat. Set the steaks out of the fridge, pat them dry and season both sides with salt and black pepper.

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Rinse the chips

Rinse the cut potatoes under cold water until the water runs mostly clear. This removes surface starch and helps the chips crisp.

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Prepare the sauce ingredients

Slice the mushrooms, finely dice the onion and crush the garlic. Keep the water, cream, mustard and thyme beside the hob.

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Parboil the chips

Put the chips in a saucepan, cover with cold water, add a good pinch of salt and bring to the boil. Simmer until the edges are just tender but the centres remain firm.

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Rough up and roast

Drain the chips thoroughly, then return them to the dry hot pan and shake gently to fluff their edges. Carefully add them to the hot tray, toss with 1 tablespoon oil and spread out in one layer. Roast, turning halfway through, until deeply golden and crisp.

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Sear the steaks

When the chips have about 10 minutes left, heat the remaining oil in a heavy frying pan over high heat until shimmering. Add the steaks and sear without moving for 2 minutes. Turn and cook for 2 minutes more for medium-rare, or adjust to your preferred doneness. Transfer to a warm plate and rest loosely covered.

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Cook the mushrooms

Lower the heat to medium. Add the mushrooms to the steak pan with a pinch of salt and cook, stirring occasionally, until browned and their moisture has evaporated. Add the onion and cook until softened, then stir in the garlic and thyme for the final minute.

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Finish the sauce

Pour in the hot water, scraping up the savoury browned bits from the base of the pan. Simmer until reduced by about half, then stir in the cream and mustard. Simmer gently until glossy enough to coat the back of a spoon. Taste and season with black pepper and salt if needed.

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Serve

Slice the rested steaks across the grain and spoon over any resting juices. Divide between warm plates with the crisp chips and pour the thyme mushroom sauce alongside or over the steak. Serve immediately.