Heat the clarified butter in a non-stick frying pan. Sauté the mushrooms and shallots for approx. 5 mins. Pour in the wine, reduce to half the amount, add the stock, cook for approx. 2 mins. Add the mascarpone, mix well and season. Stir in the parsley.
Heat 2 tbsp of the retained truffle oil in a wide-bottomed frying pan. Reduce the heat, salt the cutlets, fry on a medium heat for approx. 3 mins. on each side. Add the truffle slices, continue to cook for approx. 1 min.