01 - Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Drain, reserving ½ cup of the cooking liquid.
02 - Pat chicken breasts dry and season both sides with salt and pepper. Heat olive oil in a large skillet over medium heat. Cook chicken for 5-7 minutes per side until golden and cooked through to 165°F. Rest for 5 minutes, then slice thinly.
03 - In the same skillet, melt butter over medium heat. Add minced garlic and sauté for 1-2 minutes until fragrant. Sprinkle in flour while whisking constantly and cook for 1 minute to remove raw flour taste.
04 - Gradually whisk in milk and heavy cream. Bring to a simmer and cook, stirring continuously, for 3-4 minutes until slightly thickened. Add Parmesan cheese and red pepper flakes, stirring until smooth. Adjust consistency with reserved pasta water if needed.
05 - Add cooked pasta and sliced chicken to the sauce. Toss until evenly coated. Garnish with fresh parsley and serve immediately.