01 - Pat chicken breasts dry with paper towels. Season both sides generously with salt and pepper, then dust lightly with flour on all sides to ensure even coating.
02 - Heat olive oil in a large skillet over medium-high heat until shimmering. Place chicken breasts in the pan and sear for 4 to 5 minutes per side until golden brown and a nice crust forms. Transfer chicken to a plate and set aside.
03 - Reduce heat to medium. Add butter to the same skillet and let it melt. Add mushrooms and onion, sautéing for 5 minutes until softened and golden. Stir in garlic and cook for 1 minute until fragrant, being careful not to burn it.
04 - Pour in chicken broth, using a wooden spoon to scrape up the browned bits from the bottom of the pan. Let the mixture simmer for 2 minutes until slightly reduced.
05 - Stir in heavy cream, Parmesan cheese, and thyme. Bring the mixture to a gentle simmer, stirring constantly until the cheese melts and the sauce begins to thicken slightly.
06 - Return chicken breasts to the skillet, nestling them into the sauce. Simmer uncovered for 7 to 10 minutes until chicken is cooked through and reaches an internal temperature of 165°F. The sauce should coat the back of a spoon.
07 - Garnish with fresh parsley and serve immediately over pasta, mashed potatoes, or steamed rice.