Use thin cut chicken breasts or slice or pound regular breasts to desired thinness.
In a large skillet, melt butter and cook chicken over medium-high heat. You may need to do this in two batches. Set cooked chicken aside on a plate.
Add mushrooms, pancetta and garlic to pan and saute until mushrooms are soft.
Add marsala wine, bring to a boil, then reduce heat and simmer 3-4 minutes.
Add broth and return chicken to pan to heat through.
Serve warm and top with a sprinkle of parsley.
**Optional, for a slightly thicker sauce, mix a Tablespoon of cornstarch with a splash a water and stir until dissolved. Add when you add the broth, bring to a boil again and then reduce heat and let simmer to thicken.