Slice chicken breasts in half lengthwise. Place each piece between plastic wrap or wax paper and pound with a mallet until it’s 1/3-inch thick. Season with a bit of salt and pepper.

Saute 2 pieces at a time in the oil in a skillet over medium-high heat until browned, about 3-5 minutes. Turn and cook an additional 2 minutes. Transfer to a plate and tent with foil to keep warm. Repeat with remaining chicken.

Cook the mushrooms in the same pan over high heat—about 5 minutes or until they start to brown. Add additional oil if necessary to prevent scorching.

Deglaze the pan with the marsala wine and bring to a boil. Simmer until liquid is reduced by half-about 5 minutes.

Remove from heat and add the prosciutto, sage and butter. Add any additional salt and pepper at this time.

Pour sauce over chicken and serve.