
Heat oven to 375F. Line an 8x8 baking dish with parchment paper.
In a large bowl, beat together sugar, sour cream, butter, and eggs until creamy. Blend in bananas and vanilla extract.
Add flour, baking soda, salt, stir together until just combined. Spread batter evenly into pan.
Bake 20 to 25 minutes or until golden brown. Let cool slightly and then remove from pan using the parchment to lift.
Brown Butter in a medium saucepan, melt it over medium-high heat, letting it continue to cook until brown bits form.
Pour the butter into a heat-proof bowl and whisk. Add in the powdered sugar and vanilla and mix until smooth.
Spread the icing on the bars when they have cooled for about 10-15 minutes.