Directions

1. For filling, in saucepan cook mushrooms and onion in butter over medium-low heat until tender and liquid has evaporated, stirring frequently. Remove from heat, stir in leamon juice, rosemary, egg yolk, Romano and walnuts; set aside. Butterfly pork loin by cutting through roast horizontally to within 1/4-inch of the other side. Do not cut all the way through. Open out and pound to roughly a 6x8-inch rectangle. Spread filling evenly on meat rectangle. Roll up lengthwise; tie with kitchen string at 1-2 inch intervals to secure.
2. Place roast in shallow pan and rost in a 350 degree F. oven for 20-40 minutes (20 minutes per pound) or until internal temperature on a thermometer reads 145 degrees F. Remove roast from oven; let rest about 10 minutes. Slice to serve, removing string.