01 - Pat the chicken breasts dry and season both sides generously with salt and black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Add the chicken breasts and cook for 5–6 minutes per side until golden brown and cooked through to an internal temperature of 165°F. Remove from the skillet and set aside on a plate.
03 - Reduce the heat to medium. Add the butter to the same skillet, then sauté the onion and garlic for about 2 minutes until fragrant. Add the sliced mushrooms and cook for approximately 5 minutes until softened and golden brown.
04 - Pour in the chicken broth, scraping up any browned bits from the bottom of the skillet. Let the liquid simmer for 2 minutes to reduce slightly.
05 - Stir in the heavy cream and thyme. Simmer the sauce for 2–3 minutes, stirring occasionally, until it thickens slightly and coats the back of a spoon.
06 - Place the chicken breasts back into the skillet. Spoon the sauce and mushrooms over the chicken and simmer for 2–3 minutes until everything is heated through and the flavors meld.
07 - Sprinkle with freshly chopped parsley and serve immediately while hot.