Cook the Pasta: Bring a large pot of generously salted water to a rolling boil. Add the tagliatelle and cook according to packet instructions until al dente (usually around 8-10 minutes). Before draining, reserve at least 250ml (a large mugful) of the starchy pasta water.

Sear the Chicken: While the pasta cooks, heat the olive oil in a large, deep frying pan or sauté pan over a medium-high heat. Season the diced chicken with salt and pepper, add it to the hot pan in a single layer, and cook for 5-7 minutes, turning occasionally, until golden brown and cooked through. Remove the chicken from the pan with a slotted spoon and set aside.

Sauté the Mushrooms: Reduce the heat to medium and add the butter to the same pan. Once melted, add the sliced mushrooms. Don't overcrowd the pan; cook them in two batches if necessary. Cook for about 5-6 minutes, stirring infrequently, until they are beautifully caramelised and have released their liquid. For a guide on getting this right, check out this great article on how to cook mushrooms.

Build the Aromatic Base: Add the finely diced shallots to the pan with the mushrooms and cook for 2-3 minutes until softened and translucent. Stir in the minced garlic and cook for another minute until fragrant, being careful not to let it burn.

Deglaze and Simmer: If using, pour in the white wine to deglaze the pan, scraping up any browned bits from the bottom with a wooden spoon. Let it bubble away and reduce by about half. Pour in the chicken stock and bring to a gentle simmer.

Create the Creamy Sauce: Reduce the heat to low. Stir in the double cream and crème fraîche until well combined. Let the sauce simmer gently for 2-3 minutes to thicken slightly. Avoid boiling it vigorously.

Bring It All Together: Return the cooked chicken to the pan. Season the sauce generously with salt and freshly ground black pepper. Stir in the grated Parmesan cheese until it melts and the sauce is smooth.

Combine with Pasta: Drain the pasta and add it directly to the pan with the sauce. Add half the chopped parsley. Now, it's time to toss everything together. I find that using tongs works best to really coat every strand.

Emulsify the Sauce: This is the most important step! Add a good splash (about 60ml) of the reserved pasta water to the pan and continue to toss vigorously. The starch in the water will help the sauce emulsify, becoming glossy and clinging beautifully to the pasta. Add more water, a little at a time, until you reach your desired consistency. What works best for me is aiming for a sauce that's silky, not watery.

Serve Immediately: Divide the creamy pasta between four warm bowls. Garnish with the remaining fresh parsley and an extra grating of Parmesan cheese.