Grease and flour a 15 X 10-inch Jelly Roll pan. Preheat your oven to 375F.

In a large bowl mix together your sugar, sour cream, butter and eggs until they are creamy. Next blend in bananas and vanilla extract. Now add your flour, baking soda, salt and blend them for 1 minute. If desired stir in walnuts.

Spread the batter evenly into your pan. Bake for 20 -25 minutes until golden brown.

While your cake is baking, heat your butter in a large saucepan on medium heat until boiling. Let it turn a delicate brown and then remove from heat immediately.

Add powdered sugar, milk and vanilla extract. Whisk until your frosting is smooth. It should be thinner than frosting but thicker than a glaze.

Spread frosting over bars while they are warm. The frosting will thicken and harden making it difficult to spread on bars when cool.