01 - Pat the chicken breasts dry with paper towels. Season both sides generously with salt and freshly ground black pepper.
02 - Heat the olive oil in a large skillet over medium-high heat until it shimmers. Add the chicken breasts and cook for 5 to 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. 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 - Add the heavy cream and dried thyme to the skillet, stirring to combine. Simmer for 2 to 3 minutes until the sauce thickens slightly and coats the back of a spoon.
06 - Return the chicken breasts to the skillet, spooning the mushroom sauce over the top. Simmer for 2 to 3 minutes until the chicken is heated through and the flavors meld together.
07 - Sprinkle with freshly chopped parsley and serve hot over mashed potatoes, rice, or pasta.