1. Place veal cutlets between sheets of plastic wrap and pound with a meat mallet or rolling pin until they are 1⁄8 inch thick. Remove from the plastic and place prosciutto slices and sage leaves on each piece. Roll up the veal and secure with a toothpick.
2. Peel the onion and cut into quarters. Place in the bowl fitted with the ultrablade knife and mix at speed 11 for 10 seconds.
3. Replace the ultrablade knife with the mixer. Add oil and white wine. Launch the P1 simmer program at 270°F for 5 minutes.
4. Add the veal, tomato purée and water. Season with salt and pepper. Launch the P2 simmer program at 210°F for 20 minutes. Remove toothpicks before serving.