01 - Bring a large pot of salted water to a boil. Cook penne according to package directions until al dente. Drain and set aside, reserving 1/2 cup of pasta water for sauce adjustment.
02 - While pasta cooks, heat olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add chicken pieces, season with salt and pepper, and cook until golden and cooked through, approximately 6 to 8 minutes. Transfer to a plate and cover to keep warm.
03 - In the same skillet, reduce heat to medium. Add remaining 1 tablespoon butter and minced garlic. Sauté until fragrant, about 1 minute.
04 - Pour in heavy cream and milk, stirring to combine. Simmer gently for 3 to 4 minutes until slightly thickened.
05 - Reduce heat to low. Gradually stir in Parmesan cheese until melted and the sauce is smooth. Season with a pinch of nutmeg, additional salt, and pepper to taste.
06 - Return cooked chicken to the skillet, add drained penne, and toss to coat thoroughly. If the sauce is too thick, add a splash of reserved pasta water until achieving desired consistency.
07 - Remove from heat. Garnish with chopped parsley and serve immediately.