01 - Bring a large pot of salted water to a boil. Add the penne and cook until al dente according to package instructions. Drain, reserving 1/2 cup of pasta water.
02 - Season the chicken breasts with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Add chicken and cook for 5–6 minutes per side, or until golden and cooked through. Remove to a plate and let rest for 5 minutes, then slice thinly.
03 - In the same skillet, lower heat to medium and add butter. Once melted, add minced garlic and sauté for 1 minute until fragrant.
04 - Pour in the heavy cream and milk. Stir and bring to a gentle simmer. Add nutmeg if using. Gradually whisk in the Parmesan cheese until melted and sauce is smooth.
05 - Season the sauce with salt and pepper to taste. Add the cooked penne and sliced chicken to the skillet. Toss to coat, adding a splash of reserved pasta water if needed to loosen the sauce.
06 - Serve hot, garnished with chopped parsley and extra Parmesan.