Step 1: Prepare the Chicken

1. Season the chicken breasts with salt and black pepper.
2. Lightly dredge the chicken in all-purpose flour, shaking off any excess.

Step 2: Sear the Chicken

1. Heat olive oil in a large skillet over medium-high heat.
2. Add the chicken breasts and cook for 4–5 minutes on each side until golden brown.
3. Remove the chicken from the skillet and set aside.

Step 3: Sauté the Mushrooms

1. In the same skillet, melt the butter over medium heat.
2. Add the sliced mushrooms and cook for 5–7 minutes until browned and softened. Stir occasionally.

Step 4: Build the Sauce

1. Add the minced garlic and thyme to the skillet, cooking for 1–2 minutes until fragrant.
2. Deglaze the pan with chicken broth, scraping up any browned bits from the bottom.
3. Stir in heavy cream, Parmesan cheese, and Dijon mustard. Let the sauce simmer for 3–4 minutes until slightly thickened.

Step 5: Combine Chicken and Sauce

1. Return the chicken breasts to the skillet, spooning the sauce over them.
2. Reduce the heat to low, cover, and simmer for 10 minutes until the chicken is fully cooked (internal temperature of 165°F/74°C).

Step 6: Garnish and Serve

1. Remove from heat and sprinkle with fresh parsley.
2. Serve immediately with your choice of side dishes.