Pound the veal slightly between sheets of plastic wrap, or in a 1 gallon resealable plastic bag, to a uniform thickness of 1/8 inch, then season with salt and pepper. Layout half of the scallopinis on a clean flat work surface, and layer each with 1 thin slice of prosciutto. Fold the prosciutto to fit on the scallopini, then place 1-2 whole sage leaves on top of the prosciutto. Finish by placing another scallopini on top of the sage leaves, using toothpicks as skewers to hold together. Set up a dredging station by placing about 1 cup of flour on a flat dish, and one by one, dredge each veal package in the flour. Shake off excess placing the dredged packages on another plate.

Heat a large heavy skill over medium high heat. Add 1 tablespoon of olive oil and 2 tablespoons of butter, then saute the veal packages, a couple at a time, for 2-3 minutes on one side, and 1-2 minutes on the second side. As each group of veal is completed, transfer to a warm platter, or individual serving dishes. Keep the cooked scallopini warm in an oven until all servings are cooked. When the last of the veal has been sauteed and is being kept warm, reduce the heat to medium low. Deglaze the pan with the chicken stock, and continue cooking the stock until reduced by half. Add the wine, lemon juice, and remaining butter, and swirl until combined to form a sauce. Bring sauce to a boil and cook until slightly thickened, if the sauce fails to thicken, compound a cornstarch slurry consisting of 2 tablespoons cold water and 2 tablespoons of cornstarch. Add it to the sauce while stirring to thicken it. Remove the scaloppini from the oven, pour the sauce over the scallopini, then serve immediately.