Bring a large pot of salted water (2 tablespoons kosher salt per gallon) to boil.
Liberally season the chicken with salt and pepper then dredge the pieces in flour and shake off the excess. Place the dredged chicken pieces on a baking sheet and set aside.
Heat a very large pan to medium heat and saute the mushrooms until they brown and release their water (about 5 minutes). Season with salt and pepper, then remove mushrooms from the pan and set aside in a dish tented with foil.
Add the prosciutto to the same pan and cook until browned (about 3-4 minutes). Remove the prosciutto to a small plate and set it aside.
Add 1 tablespoon of butter and 1 tablespoon of olive oil to the pan. Sear the chicken until browned on both sides (about 6-7 minutes total) then remove the pieces to the same plate as the mushrooms. If necessary, work in batches using more butter and olive oil so as to not crowd the chicken.
At this time begin cooking the pasta to 1 minute less than al dente.
Add the garlic to the pan along with a touch more olive oil and cook until golden (about 1 minute). Add the marsala and the chicken stock and turn the heat to high. Reduce the liquid by about half (3 minutes) while scraping the pan with a wooden spoon to remove all of the flavor bits.
Once the sauce adequately reduces, turn the heat down to medium-low, add the remaining butter, and whisk it in.
Add all the chicken, mushrooms, and half the prosciutto and mix once more. Taste test the sauce and adjust salt and pepper if required.
Add the pasta to the pan and toss to coat. Cook until the pasta just reaches al dente (about 30-60 seconds). If needed, add a ladle or two of pasta water to loosen up the sauce.
Remove the pan from the heat and sprinkle in the parsley. If the pasta dries up, just add a touch more of the reserved pasta water to thin it out. Divide into plates and top with the remaining crispy prosciutto. Enjoy!