Heat oven to 350°F. Spray 9-inch square pan with nonstick cooking spray. In large bowl, combine sugar and margarine; beat until well blended. Add bananas, vanilla and egg; mix well.
Add flour, baking powder, baking soda and 2 teaspoons ginger to margarine mixture; mix until moistened. Add milk; mix well. Pour into sprayed pan.
Bake at 350°F. for 25 to 35 minutes or until toothpick inserted in center comes out clean. Cool slightly.
In small bowl, combine all topping ingredients; mix gently. Cut cake into squares; serve warm or cool topped with whipped topping mixture.