Step 1Have butcher remove all turkey bones and butterfly meat to spread out into a flat sheet. With a sharp knife, make 6 random incisions in breast and place garlic half in each. Sprinkle with salt and pepper to taste. Cover with a layer of prosciutto slices.
Step 2Beat eggs with salt and pepper to taste. Stir in parsley. Heat 1 to 2 tablespoons butter in large nonstick skillet over medium heat. Pour in eggs and cook to soft, whole round omelet or frittata (do not overcook), 2 to 3 minutes. Cool slightly. Place omelet over prosciutto.
Step 3Top with mortadella slices. Roll breast as tightly as possible, jellyroll fashion, and tie with string all around. If using fresh rosemary, insert sprigs under strings; if using dried rosemary, rub turkey roll with dried herb. Season to taste with salt and pepper.
Step 4Heat oil in large Dutch oven or roasting skillet over low heat. Add turkey roll and cook to brown evenly, turning occasionally. Increase heat and sprinkle with wine. After about 5 minutes or after wine has evaporated, add 1/3 cup butter, onion and shallot. Reduce heat to low, cover and simmer 1 hour or until meat thermometer inserted in roll reaches 165 degrees. Baste top occasionally.
Step 5Let stand about 15 minutes before carving. Cut into thin slices and arrange on serving platter. At time of serving, heat sauce and pour some over slices and pass remainder.