01 -
Preheat the oven to 190°C. Line an 20x20 cm baking dish with parchment paper.
02 -
In a large bowl, beat together granulated sugar, sour cream, softened butter, and egg until the mixture is creamy. Stir in mashed bananas and vanilla extract.
03 -
Add flour, baking soda, and salt to the wet mixture. Stir gently until just combined. Spread the batter evenly into the prepared pan.
04 -
Bake for 20 to 25 minutes or until the top is golden brown and a toothpick inserted comes out clean. Allow to cool slightly, then lift from the pan using the parchment paper.
05 -
Melt butter in a medium saucepan over medium-high heat. Continue cooking until butter turns golden brown and develops a nutty aroma. Immediately transfer browned butter to a heatproof bowl and whisk to cool slightly.
06 -
Whisk powdered sugar and vanilla extract into the browned butter until smooth. Spread the icing over the bars after they have cooled for 10 to 15 minutes.