1Heat oven to 300. Spray a springform pan lightly w/ cooking spray. In bowl combine graham cracker crumbs, brown sugar, and butter. Press into bottom and sides of pan.
2In lg bowl, combine 1/2 cup sugar and flour. Add vanilla, cream cheese and eggs. Beat until smooth. Add milk, sour cream, lemon juice, orange juice, lemon peel and orange peel. Beat until smooth. In another bowl, beat egg whites until soft peak forms. Add 1/4 cup sugar, a little at a time. Gently fold into cream cheese mix.
3Pour mix into crust. Bake 1 hr or until set. Cover, chill for 4 hrs. Sprinkle top of cheesecake w/ lemon peel and orange peel.