Chicken Breasts filled with Prosciutto di Parma and Fontina

1. Place each chicken breast half between 2 pieces of plastic wrap. Using a meat pounder or bottom of a small heavy saucepan, pound until 1/4 inch thick; remove plastic wrap.
2. With the rough side of the chicken breast facing up, top each with 1/4 of the Prosciutto di Parma, cutting to fit. Sprinkle each with 1/4 cup cheese, 1Tbsp. walnuts and 3 sage leaves, leaving a 1/4-inch border. Roll up jelly-roll style; wrap tightly in plastic wrap. Refrigerate chicken for at least 1 hour.
3. Unwrap chicken; secure rolls with toothpicks; sprinkle with salt and pepper, dividing evenly.
4. In a large skillet over medium heat, heat oil until hot. Add chicken; cook until golden brown on all sides, turning frequently, about 7 minutes.
5. Add wine; simmer, covered, until chicken is cooked through, 10 to 15 minutes. Remove chicken to a cutting board; keep warm.
6. Over medium-high heat, cook wine until reduced to 2/3 cup. Strain into a small bowl. Slice each chicken roll into thin slices; serve drizzled with wine sauce.