Cook the pasta.
Bring a large pot of well-salted water to a boil. Add the fettuccine and cook until al dente, according to the package instructions. Before draining, reserve about ½ cup of the pasta water, then set the pasta aside.
2. Season the chicken.
Pat the chicken dry with paper towels, then season both sides with salt and black pepper. If the chicken breasts are thick, slice them in half horizontally so they cook faster and more evenly.
3. Sear the chicken.
Heat the olive oil and butter in a large skillet over medium-high heat. Once hot, add the chicken and cook for 7 to 9 minutes per side, or until golden brown and cooked through. Transfer to a plate and let it rest for a few minutes before slicing.
4. Start the Alfredo sauce.
In the same pan, lower the heat to medium and add the butter, heavy cream, and minced garlic. Stir gently as the butter melts and the garlic softens. Let the sauce warm through slowly for a few minutes without boiling.
5. Add the Parmesan.
Season the sauce with salt and black pepper. Add the Parmesan a little at a time, stirring well after each addition until the sauce is smooth, creamy, and glossy.
6. Toss the pasta.
Add the drained fettuccine to the skillet and toss until the pasta is fully coated in the sauce. If the sauce feels too thick, add a splash of the reserved pasta water until it becomes silky and easy to coat.
7. Finish and serve.
Slice the chicken and place it over the creamy Alfredo pasta. Garnish with chopped parsley and a little extra Parmesan, then serve straight away while hot and creamy.
A Few Notes
The secret to a really good Chicken Alfredo is keeping the sauce gentle. Do not let it boil, or it can lose that smooth, velvety texture. Freshly grated Parmesan also makes a big difference, both in flavour and in how well the sauce melts.
If you want to make it your own, you can add broccoli, mushrooms, spinach, or even sun-dried tomatoes. Garlic bread and a crisp green salad are perfect on the side.