Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package directions until al dente. Reserve a cup of the pasta water before draining the pasta.

Meanwhile, heat the olive oil in a large skillet over medium-high heat. Add the onions and garlic and cook for 3-4 minutes until softened.

Add the ground beef to the skillet and cook for 4-5 minutes, breaking it apart with your spoon as you go, until browned.

Add the sliced mushrooms to the skillet and cook until they soften and release their liquid. Deglaze the pan with the dry white wine, scraping up any browned bits stuck to the bottom.

Stir in the chicken stock and the Italian seasoning mix. Bring to a simmer and cook for a few minutes to reduce the liquid slightly. Stir in the heavy cream and reduce heat to low.

Add the cooked fettuccine to the sauce and toss to coat thoroughly. Add the grated Parmesan cheese and as much of the reserved pasta water as you need to reach your desired consistency.

Stir in most of the parsley, reserving some for garnish. Adjust salt and pepper if needed. Serve immediately, garnished with the remaining parsley and extra Parmesan cheese.