1) If you are starting with whole chicken breasts, cut them in half horizontally, then pound them out until they are an even thickness. One breast will make two cutlets.
2) Dry off cutlets well with a paper towel.
3) Dredge cutlets in flour and season with salt and pepper. Sprinkle diced sage on top of each cutlet.
4) Press one large piece of prosciutto onto each cutlet over the sage. Press down on it so the prosciutto sticks to the cutlet.
5) Heat oil in a large skillet over medium-high heat. Once hot, add cutlets, prosciutto side down first. Cook for 4-5 minutes on that side and flip. The prosciutto should be browned and adhered to the chicken.
6) Cook on the second side until the chicken is cooked through or you can transfer to a 350 degree F. oven to finish cooking the chicken until it reaches 165 degrees F. Once cooked, you can remove the chicken from the skillet and make the sauce.
7) Turn heat down to medium for your skillet that you cooked the chicken in. Add white wine and lemon juice and use the liquid to scrape up any bits stuck to the pan.
8) Let the sauce simmer for a few minutes and then stir in butter, one tablespoon at a time. Add chopped parsley right at the end.
9) Serve chicken drizzled with sauce or toss sauce with spaghetti before serving.