01 - Season chicken breasts thoroughly with salt and pepper on all sides. Dredge each piece lightly in flour, shaking off any excess coating.
02 - Heat olive oil in a large skillet over medium-high heat until shimmering. Sear chicken breasts for 4-5 minutes per side until golden brown and cooked through. Transfer to a plate and cover loosely with foil to rest.
03 - Return skillet to medium heat. Add mushrooms and onion, cooking for 4 minutes until softened and lightly browned. Add minced garlic and cook for 1 additional minute until fragrant.
04 - Pour chicken broth into the skillet, using a wooden spoon to scrape up browned bits from the bottom. Stir in heavy cream, Dijon mustard, dried thyme, and rosemary. Bring mixture to a gentle simmer.
05 - Return chicken breasts to the skillet, nestling them into the sauce. Simmer for 5-7 minutes until sauce thickens slightly and chicken is heated through.
06 - Stir fresh parsley into the sauce. Taste and adjust seasoning with additional salt and pepper if needed. Serve chicken immediately with generous sauce, garnished with extra parsley.