Place chicken breasts on a cutting board and cover with plastic wrap.
Use a meat tenderizer or rolling pin to flatten the chicken until it's about 1/4-inch thick. Set aside.
Mix cake flour, salt, pepper, rosemary, oregano, and thyme in a bowl.
Heat olive oil in a pan over medium-high heat.
Coat the chicken in the seasoned flour, shaking off any excess.
Cook the chicken in the pan for 4-5 minutes per side until golden brown. Drain on paper towels.
In the same pan, add more olive oil if needed. Sauté garlic and onions until translucent.
Add mushrooms and cook for 5 minutes. Season with salt and pepper.
Pour in Marsala wine and let it cook for a minute to remove alcohol.
Add chicken stock and simmer for 2-3 minutes until slightly thickened.
Return chicken to the pan, add butter, and simmer for 3-5 minutes.
Serve immediately, garnished with parsley.