Add 1 tablespoon of oil to the skillet. Add the shallot and garlic. Saute until fragrant, about 30 seconds. Add a tablespoon of the olive oil, if necessary. Add the mushrooms and saute until tender and the juices evaporate, about 3 minutes. Season with salt. Add the Marsala. Simmer until the Marsala reduces by half, about 2 minutes. Add the broth and the rosemary leaves. Simmer until reduced by half, about 4 minutes. Return the veal to the skillet. Pour in all of the pan juices. Cook just until heated through, turning to coat, about 1 minute. Stir the remaining 1 tablespoon of butter into the sauce. Season the sauce with salt and pepper, to taste.