Banana Nut Cheesecake

1 cup chocolate wafer crumbs
1/4 cup butter or margarine, melted
2 (8-ounce) packages cream cheese, softened
1/2 cup granulated sugar
1/2 cup mashed banana
2 large eggs
1/4 cup walnuts, chopped
1/3 cup semisweet chocolate chips
1 tablespoon butter or margarine
2 tablespoons water

Combine chocolate wafer crumbs and 1/4 cup melted butter; press onto the bottom of a 9-inch springform pan. Bake at 350°F (175°C) for 10 minutes. Remove from the oven and cool. In a large mixing bowl, combine softened cream cheese, sugar, and mashed banana; mixing at with an electric mixer on medium speed until well blended. Add eggs, one at a time, mixing well after each addition. Stir in chopped walnuts and pour over the crust. Bake at 350°F (175°C) for 40 minutes. Loosen the cake from the rim; cool before removing from the pan. Melt together chocolate chips, 1 tablespoon butter, and water over low heat, stirring until smooth. Drizzle over the cheesecake. Chill. Makes 12 servings.