Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Just before draining, reserve about 250ml (a mugful) of the starchy pasta water. Drain the pasta and set aside.

While the pasta is cooking, season the chicken pieces generously with salt, pepper, and the onion powder. Heat the olive oil in a large, non-stick frying pan or skillet over a medium-high heat. Add the chicken and cook for 6-8 minutes, turning occasionally, until golden brown and cooked through. Remove the chicken from the pan and set aside on a plate.

Reduce the heat to medium-low. Add the minced garlic to the same pan and cook for about 30 seconds until fragrant, being careful not to let it burn.

In a small bowl, whisk the cornflour with 2 tablespoons of the cold skimmed milk until you have a smooth paste. Pour the remaining milk into the pan with the garlic, then whisk in the cornflour slurry.

Bring the milk mixture to a gentle simmer, whisking continuously. Let it bubble gently for 1-2 minutes until it has thickened slightly. It should be thick enough to coat the back of a spoon.

Remove the pan from the heat completely. This step is crucial. Let it cool for a minute. Add the room-temperature Greek yoghurt and the freshly grated Parmesan cheese. Stir or whisk until the cheese has melted and the sauce is smooth and creamy. What works best for me is to add the cheese in two batches to ensure it melts evenly. Season with the nutmeg, and add salt and pepper to taste.

Return the cooked pasta and chicken to the pan with the sauce. Toss everything together gently until the pasta and chicken are well-coated. If the sauce is too thick, add a splash of the reserved pasta water until you reach your desired consistency. The starch in the water helps the sauce emulsify and cling to the pasta.

Serve immediately, garnished with a generous sprinkle of fresh parsley and an extra grating of Parmesan, if you like.