01 -
Heat the oven to 190°C. Line a 20x20 cm pan with parchment paper for easy removal.
02 -
Grab a big bowl and mix softened butter, sugar, sour cream, and egg until smooth. Then fold in mashed bananas and vanilla.
03 -
Toss in flour, salt, and baking soda. Stir just enough to blend everything. Pour the batter into your lined pan and spread it out.
04 -
Put it in the oven for about 20 to 25 minutes. Check it by poking with a toothpick; if it comes out clean and the top's golden, it’s done. Let it cool a bit then lift it out using the parchment.
05 -
Melt butter on medium-high and keep cooking until it smells nutty and turns golden brown. Take it off heat and whisk it in a heatproof bowl to cool a little.
06 -
Stir powdered sugar and vanilla into the browned butter until smooth. Spread this over the bars once they're cooled for 10 to 15 minutes.