Heat oven to 375°F. Spray 8-inch square (2-quart) baking dish with nonstick cooking spray.
Cook pasta to desired doneness as directed on package. Drain; rinse with cold water to cool.
Meanwhile, heat oil in medium skillet over medium heat until hot. Add garlic and prosciutto; cook 2 to 3 minutes or until garlic is light golden brown.
In medium bowl, combine 1/2 the prosciutto mixture with ricotta cheese, Parmesan cheese, basil and egg; mix well. Stir spaghetti sauce into prosciutto mixture remaining in skillet.
Spoon ricotta mixture into cooked shells; place in sprayed baking dish. Spoon spaghetti sauce mixture over shells. Cover with foil.
Bake at 375°F. for 35 to 40 minutes or until mixture is thoroughly heated.