Mix the flour, salt, and pepper in a shallow dish.
Dredge the chicken breasts in the flour mixture, ensuring they are evenly coated.
Heat 2 tablespoons of olive oil in a large skillet over medium heat.
Add the chicken breasts and cook until they are golden brown on each side, about 3-4 minutes per side.
Remove the chicken and set it aside.
Add the remaining olive oil and butter to the skillet.
Sauté the mushrooms and prosciutto until the mushrooms are browned and the prosciutto is crispy.
Pour in the Marsala wine and chicken stock, and let it simmer until reduced by half.
Return the chicken breasts to the pan and cover with the sauce.
Cook the chicken in the sauce for an additional 5 to 7 minutes, or until fully cooked through.
Sprinkle with chopped parsley before serving.