Step 1: Prepare the Chicken

1. Place the chicken breasts between two sheets of plastic wrap.
2. Use a meat mallet to pound them to about 1/4-inch thickness.
3. Season both sides with salt and black pepper.
4. Dredge the chicken in all-purpose flour, shaking off the excess.

Step 2: Sear the Chicken

1. Heat olive oil and 1 tablespoon butter in a large skillet over medium-high heat.
2. Add the chicken and cook until golden brown, about 3-4 minutes per side.
3. Transfer the chicken to a plate and set aside.

Step 3: Cook the Mushrooms & Aromatics

1. In the same skillet, melt another 1 tablespoon butter.
2. Add the mushrooms and cook until tender (about 5 minutes).
3. Stir in the garlic and shallots, cooking until fragrant.

Step 4: Deglaze with Marsala Wine

1. Pour in the Marsala wine, scraping up browned bits from the skillet.
2. Let it simmer for 2 minutes to cook off the alcohol.
3. Add chicken broth and thyme, stirring to combine.

Step 5: Simmer the Sauce

1. Lower the heat and let the sauce reduce for 5 minutes.
2. Stir in heavy cream (if using) and return the chicken to the pan.
3. Simmer for another 5 minutes, coating the chicken with the sauce.

Step 6: Garnish & Serve

1. Remove from heat and sprinkle with fresh parsley.
2. Serve immediately with pasta, mashed potatoes, or roasted vegetables.