Combine crumbs and margarine; press onto bottom of the 9-inch springform pan. Bake at 350 degrees F., 10 minutes. Combine cream cheese, sugar, and flour, mixing at medium speed on electric mixer until well blended. Add eggs, one at a time, mixing well after each addition. Blend in sour cream and vanilla. Stir in chocolate chips and pour into crust. Bake at 350 degrees F., 55 minutes. Loosen cake from rim of pan; cool before removing rim of pan. Chill. Garnish with whipped cream and fresh mint leaves, if desired.