Preheat the oven to 350° and lightly butter a 9-by-13-inch baking dish. In a large, deep skillet, melt the 2 tablespoons of butter in the oil. Add the shallots and cook, stirring, for 1 minute. Add the mushrooms, season with salt and pepper and cook over high heat, stirring occasionally, until the mushrooms are browned, about 18 minutes. Add the wine and boil until evaporated, about 1 minute. Add 2 cups of the cream and bring to a boil. Simmer over moderate heat until slightly reduced, about 5 minutes. Stir in the parsley and season with salt and pepper.