Heat olive oil in a large skillet over medium heat. Season the sliced chicken with salt and pepper. Sear for 3–4 minutes on each side until golden brown. Remove from the pan and set aside.
In the same pan, add baby potatoes and cook for 5–7 minutes until lightly browned. Stir in the chopped onion and garlic, cooking until fragrant.
Pour in the chicken broth and scrape the bottom of the pan. Stir in the Dijon mustard, heavy cream, and thyme. Simmer for 3–4 minutes until slightly thickened. For another creamy dish, try Chicken Alfredo Casserole.
Return the seared chicken to the pan, stirring to coat in the sauce. Sprinkle in Parmesan cheese and let it cook for another 2–3 minutes until everything is well combined.