Cut each chicken breast in half lengthwise to make a total of 6 pieces.
Place each piece between plastic wrap and pound them to about 1/4-inch thickness.
Mix the flour with salt and pepper in a shallow dish.
Dredge the chicken in the flour mixture, shaking off any excess.
Heat olive oil in a skillet over medium-high heat.
Cook the chicken pieces in batches for about 4 minutes per side until golden.
Transfer the chicken to a plate and set aside.
In the same skillet, add garlic and mushrooms, cooking for about 2 minutes.
Pour in Marsala wine and chicken broth, letting it simmer for 5 minutes.
Stir in heavy cream and return the chicken to the skillet.
Let it cook for another 5 minutes, allowing the sauce to thicken slightly.