Pound the chicken breasts down to about a quarter inch thick, season them with salt and pepper. Lightly coat with flour and brown them in 2 tablespoons unsalted butter and 2 tablespoons olive oil. Set them aside and keep warm. Wilt some sliced shallots while deglazing the pan with a little of the wine.
Throw as many mushrooms as you'd like in the pan, give them some salt and pepper. Then cook them till they release their moisture and it evaporates. Add a half cup chicken stock and reduce by half. Then add a half to one cup Marsala wine and reduce again. I reduce it down till there's enough sauce to coat the pasta. Swirl in another 2 tablespoons unsalted butter and the sauce is finished. Slide your chicken back into the pan and serve!