Bring a large pot of water to a boil and salt it generously. Cook 1 lb fettuccine per package directions. Before draining, scoop out and set aside 1 cup of pasta water. Drain pasta and set aside.

Season both sides of 1.5 lbs chicken breasts with 1/2 tsp salt, 1/4 tsp black pepper, and 1/2 tsp garlic powder. Pound the thicker parts so the breasts are even.

Heat 1 tbsp olive oil in a large skillet over medium-high heat. When hot, add the chicken. Cook 5–7 minutes per side until golden and the internal temperature reads 165°F (74°C). Transfer to a plate and let rest 5 minutes, then slice thinly.

Reduce heat to medium. In the same skillet, melt 1/2 cup unsalted butter. Add 4 cloves minced garlic and cook about 30 seconds until fragrant — do not brown.

Slowly whisk in 2 cups heavy cream and bring to a gentle simmer. Cook 3–4 minutes to slightly reduce and thicken.

Reduce heat to low. Gradually whisk in 1.5 cups freshly grated Parmesan until the sauce is smooth. Stir in 1/4 tsp freshly grated nutmeg and the remaining 1/2 tsp salt and 1/4 tsp pepper. Taste and adjust seasoning.

Add the drained fettuccine and sliced chicken to the skillet. Toss to coat. If the sauce is too thick, add reserved pasta water a tablespoon at a time until you reach the desired consistency.

Serve immediately, garnished with 2 tbsp chopped fresh parsley.