1. Heat a grill to medium. Oil the grates, or coat them with cooking spray.
2. In a large bowl, whisk together the egg, garlic powder, mustard powder, paprika, black pepper, and salt. Set aside.
3. In a food processor, combine the turkey and prosciutto. Pulse until the meat is well chopped but still chunky, about 10 seconds total. Scrape the sides of the bowl and pulse again if any large pieces remain unchopped.
4. Transfer the meat to the bowl with the egg mixture, then mix well. Form the meat into 4 loose patties. They will be moist and not hold together well.
5. Use a spatula to carefully place burgers on the grill and cook, covered, for 4 to 5 minutes. Flip - they should be firm enough to move easily now - and cook for another 4 to 5 minutes, or until 165 degrees at the center. Top each burger with one ounce of cheese, then serve on a bun.
Note: This technique produces truly moist burgers. Although the patties are messy to form, they hold together fine on the grill.
Per serving: 420 calories; 130 calories from fat; 15 g fat ; 145 mg cholesterol; 23 g carbohydrate; 52 g protein; 1 g fiber; 1070 mg sodium.