Prepare Mushrooms: Clean and thinly slice the button mushrooms.

Chop Onions: Finely chop the yellow onions.

Slice Prosciutto: Cut the prosciutto into thin strips.

Heat the Butter: In a saucepan, melt the unsalted butter over medium heat.

Saute: Add the finely chopped onions and sliced mushrooms to the melted butter. Sauté until the onions are translucent and the mushrooms are tender.

Add Flour: Sprinkle the flour over the mushroom and onion mixture, stirring continuously to form a smooth paste.

Cook Prosciutto: Add the sliced prosciutto to the pan, allowing it to cook for a minute or two, infusing its flavor into the mixture.

Pour Marsala Wine: Pour the Marsala cooking wine into the pan, stirring to combine with the mushroom mixture.

Add the Broth: Pour the chicken broth into the pan, continuing to stir until all ingredients are well incorporated.

Simmer: Allow the Marsala sauce to simmer over medium heat for about 10-15 minutes or until it thickens to your desired consistency.

Add Seasoning: Taste the sauce and adjust the seasoning, adding salt and pepper according to your preference.

Serve: Once the Marsala sauce reaches the desired thickness, remove it from the heat. It’s now ready to be served over your favorite protein, such as chicken or veal.