For the cake batter:

1. Grease an 8 inch square pan.
2. Whisk together the flour, soda and salt in a medium bowl.
3. Cream together butter and sugar in a large mixing bowl until light and fluffy.
4. Add in half of the flour and then add the bananas, yogurt and vanilla. Add the remaining flour, nuts and chips.
5. Mix until evenly moistened.
6. Transfer the batter to the prepared pan.

To make the topping:

1. Combine all the dry ingredients (except nuts) in a bowl.
2. Stir in the melted butter until the moisture forms large crumbs. Stir in chopped nuts.
3. Sprinkle the topping over the batter in the pan.
4. Bake until the edges pull away from the pan and a cake tester inserted in the center comes out clean - abt 30-45 minutes.
5. Remove and place on a rack to cool for 20 minutes before serving warm as it is or with ice cream.

Courtesy: http://chefinyou.com/