Preheat your oven to 350 degrees. This temperature is perfect for baking your bars evenly. Ensure your oven is fully heated before placing the batter inside.
Coat a 15-inch x 10-inch x 1-inch jelly roll pan with nonstick cooking spray. This will prevent the bars from sticking and make for easy removal once baked.
In a medium bowl, whisk together 2 cups all-purpose flour, 1 teaspoon baking soda, and 1/8 teaspoon salt. This dry mixture is essential for the structure and flavor of your bars.
In a stand mixer fitted with the paddle attachment, or with an electric hand mixer on medium-high speed, beat 1/2 cup softened butter and 2 cups granulated sugar until pale and fluffy, about 2 minutes. This process incorporates air, making the bars light.
Add the 3 eggs and beat until well incorporated. They add moisture and richness to the batter.
Beat in the 1 1/2 cups mashed ripe banana and 2 teaspoons vanilla extract until fully combined. This step infuses your batter with delicious banana flavor.
Reduce the mixer speed to low and gradually add the flour mixture. Mix until uniformly combined, ensuring not to overmix; this keeps your bars tender.
Spread the batter evenly into the prepared pan. Use a spatula to ensure it’s level.
Bake for about 30 to 35 minutes, or until a toothpick inserted in the center comes out clean with a few crumbs attached. This is crucial to avoid overbaking your bars.
Once baked, remove from the oven and cool completely in the pan for at least 30 minutes. This helps set the bars.
In a stand mixer, beat 1 (8 ounce) package of softened cream cheese and 1/2 cup softened butter until smooth. This creates the creamy frosting.
Reduce the mixer speed to medium-low and gradually add 4 cups powdered sugar and 1 teaspoon vanilla extract. Beat well until fluffy.
Spread the cream cheese frosting evenly over the cooled bars. The frosting is the perfect finishing touch to your delicious creation!