Sirloin Steak & Creamy Truffle-Mushroom Sauce

While the carrots are roasting, bring a medium saucepan of lightly salted water to the boil. Peel the potato and cut into 2cm chunks. Add the potato to the boiling water and cook until easily pierced with a knife, 10-15 minutes. Drain and return to the saucepan. Add the milk, butter and the salt to the potato. Mash with a potato masher or fork until smooth. Finely chop the chives. Stir the chives through the potato. Cover to keep warm.

While the potato is cooking, finely chop the brown onion (see ingredients). Trim the woody ends of the asparagus. Thinly slice the button mushrooms. Heat a large frying pan over a medium-high heat. Add the pine nuts and toast, tossing, until golden, 2-3 minutes. Transfer to a small bowl. Return the frying pan to a medium-high heat with a drizzle of olive oil. Add the asparagus and a splash of water, then season with salt and pepper. Cook, tossing, until tender, 5-6 minutes. Transfer to a plate and cover to keep warm.

Return the frying pan to a high heat. Drizzle the sirloin steak with olive oil and season with salt and pepper on both sides. When the oil is hot, cook the steak for 2 minutes on each side for medium-rare or cooked to your liking. Using tongs, sear the fat until golden, 30 seconds. Transfer to a plate, cover and leave to rest for 5 minutes.

While the steak is resting, finely chop the garlic. Return the frying pan to a medium-high heat with a drizzle of olive oil. When the oil is hot, add the onion and sliced mushrooms and cook until softened, 2-3 minutes. Add the garlic and cook until fragrant, 1 minute. Reduce the heat to low and stir through the longlife cream (see ingredients), any steak resting juices and the truffle oil (see ingredients). Season with salt and cook, stirring, until thickened, 2-3 minutes. TIP: Use less of the truffle oil if you're not a fan of the strong flavour.