Preheat the oven to 350°. On a large cutting board, cut each veal tenderloin into two 4-ounce medallions. Cover with plastic wrap and pound them thin with a mallet, about ¼ inch thick. Season with salt and pepper.
Place a slice of cheese on top of each piece of veal, then add a slice of ham, and repeat the process two more times.
In three separate shallow bowls, add the flour, eggs and panko. Carefully coat each cordon bleu with flour, then in the eggs, and then cover with breadcrumbs on both sides.
In a medium sauté pan, heat the oil. Add the veal cordon bleu and cook over moderate heat, turning once, until golden brown and cooked through, about 10 minutes. Serve with thinly sliced lemon and enjoy!