01 - Pat chicken breasts thoroughly dry with paper towels. Season both sides evenly with salt and black pepper. Lightly dust each breast with flour, shaking off excess.
02 - Heat olive oil in a large skillet over medium-high heat until shimmering. Place chicken breasts in pan and sear for 4-5 minutes per side until deep golden brown. Transfer to plate and set aside.
03 - Reduce heat to medium. Add butter to skillet and melt. Add sliced mushrooms and chopped onion. Sauté for 5 minutes until softened and lightly golden. Add minced garlic and cook 1 minute until fragrant.
04 - Pour chicken broth into skillet, scraping bottom with wooden spoon to release browned bits. Let simmer for 2 minutes until slightly reduced.
05 - Stir in heavy cream, grated Parmesan, and dried thyme. Bring to gentle simmer, stirring constantly until cheese melts and sauce begins to thicken slightly.
06 - Return chicken breasts to skillet, nestling into sauce. Simmer uncovered for 7-10 minutes until chicken is cooked through and sauce reaches desired consistency.
07 - Sprinkle with fresh parsley and serve immediately over pasta, rice, or mashed potatoes.