Cut a deep pocket in each half of chicken breast, being careful not to cut all the way through. In each pocket place cheese pieces and a sprig of sage, or ⅛ teaspoon dried sage. Cover and chill 2 hours or longer. Combine eggs, Parmesan cheese, salt, pepper, and parsley in large bowl and beat thoroughly. Roll chilled chicken pieces in flour, then dip in egg mixture; repeat twice. Heat butter in heavy skillet and saute breasts until crisp, then bake in oven 10 to 15 minutes at 375 degrees F to cook breasts through, melt cheese, and brown coating.