01 - Season chicken breasts evenly on both sides with salt and black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Add chicken breasts and sear for 4 to 5 minutes per side until golden brown and cooked through. Remove to a plate and cover loosely with foil.
03 - In the same skillet, melt butter. Sauté chopped onions for 2 minutes until softened. Add sliced mushrooms and cook for 5 to 6 minutes, stirring occasionally, until golden and liquid evaporates.
04 - Add minced garlic and thyme leaves to the skillet. Cook for 1 minute until fragrant.
05 - Pour in chicken broth, scraping up any browned bits from the pan. Simmer for 2 to 3 minutes to reduce slightly.
06 - Stir in heavy cream and bring to a gentle simmer. Cook for 3 to 4 minutes until the sauce thickens slightly.
07 - Return chicken breasts to the skillet. Spoon sauce and mushrooms over the top. Simmer for 2 to 3 minutes until heated through.
08 - Sprinkle chopped fresh parsley over the dish before serving.