Heat oven to 350 degrees. Lightly grease and flour bottom only of an 8-inch square pan. Mix together banana, flour, sugar, egg, walnuts, vanilla, baking powder and salt in medium mixing bowl.
In 2-quart saucepan, melt chocolate chips, oil and margarine over low heat, stirring constantly. Add flour mixture and stir well with wooden spoon. Spread batter evenly in pan. Bake 25 to 28 minutes; let cool on wire rack. Cut into 2-inch squares.
Recipe submitted by Paul G on 11/29/99