Place chicken between 2 sheets of plastic wrap and use mallet to pound chicken to 1/3-inch thickness (sub scallopini if desired). Sprinkle chicken with salt and pepper (I always use kosher and fresh ground). Spread 1/2 cup flour on plate. Turn chicken in flour to lightly coat both sides, make sure to shake off excess.
Melt butter with oil in large skillet over medium-high heat. Add chicken cook 3-4 minutes. Turn chicken over and cook just until almost cooked through, about 2-3 minutes. Transfer to platter and cover to keep warm; reserve skillet.
Over medium high heat wine and chicken stock to deglaze the pan by scraping up the chicken bits off the bottom for roughly 1 minute Season to taste with salt and pepper. Simmer over meduim heat for 5-7 mins to thicken the sauce. You can always mix 1 tbls of flour and 1 tbls of water together and add it to the sauce if you don't feel it is thick enough.
While the sauce simmers place 2 prosciutto slices on each piece of chicken and top with 1-2 pieces of cheese (amount will depend on size of cheese slices). Then place the chicken back into the pan with the sauce and sprinkle the sage leaves around the pan. Squeeze the lemon or add the lemon juice to the pan and cover with lid. Simmer the chicken breast with the sauce for 2 mins or until the cheese is melted fully.
Plate the chicken on and long narrow plate and drizzle the sauce over the chicken pieces and serve with your favorite rice or orzo on the side. Oh yeah -- Enjoy!