Preheat oven to 425°.
Lightly coat 6 (8-ounce) soufflé dishes with cooking spray; sprinkle evenly with breadcrumbs. Set aside.
Combine milk and polenta in a medium saucepan, stirring with a whisk. Bring to a boil, stirring constantly. Reduce heat; simmer 4 minutes or until thick. Remove from heat. Add cheese and prosciutto, stirring until cheese melts.
Beat egg whites with a mixer at high speed until stiff peaks form (do not overbeat). Gently stir one-fourth of egg whites into polenta mixture; gently fold in remaining egg whites. Gently spoon mixture into prepared dishes; arrange dishes on a baking sheet. Place spoon breads in oven. Immediately reduce oven temperature to 350°. Bake at 350° for 25 minutes or until spoon breads are set. Serve immediately.