1/2 cup unsalted butter, melted
1/2 cup firmly packed brown sugar
1/4 cup white sugar
1 tsp ground cinnamon
1/2 tsp salt
1/4 tsp ground nutmeg
1 cup mashed banana
1 large egg yolk
1 1/2 tsp vanilla extract
1 1/4 cups all-purpose flour
1/4 tsp baking soda
1/2 cup chopped walnuts
Step 1: Preheat the oven to 350 degrees. Line an 8×8-inch square pan with enough parchment paper to have overhang on all sides.
Step 2: Combine In a large bowl, whisk together butter, brown sugar, white sugar, cinnamon, salt, and nutmeg until smooth and combined. Add in mashed banana, egg yolk, and vanilla and mix until thoroughly incorporated. Add in flour and baking soda and whisk until just combined. Stir in walnuts. Pour batter into the prepared pan and smooth in an even layer.
Step 3: Bake in the preheated oven until the edges of the bars are golden and the center of the bars is set, about 30 to 35 minutes. Allow bars to cool in the pan for 10 minutes before removing to a wire rack to cool completely
