Crust: Combine crumbs and butter; press onto bottom of 9-inch springform pan. Bake at 350F. 10 minutes.

Filling: Combine cream cheese, sugar and banana, mixing at medium speed on electric mixer until well blended. Add eggs, one at a time, mixing well after each addition. Stir in walnuts; pour over crust. Bake at 350F. 40 minutes. Loosen cake from rim of pan; cool before removing rim of pan.

Topping: Melt chocolate pieces and butter with water over low heat, stirring until smooth. Drizzle over cheesecake. Chill.