Instructions

• Preheat the oven to 350°F. Line a 9x13-inch pan with parchment paper so two opposite sides overlap to form handles; lightly spray the parchment with non-stick spray and set the pan aside.
• In a large bowl combine 1/2 cup packed light brown sugar, 1/2 cup granulated sugar, 1 cup very ripe mashed banana, 1 teaspoon pure vanilla extract, 1/3 cup canola oil (or melted coconut oil), and 2 large room-temperature eggs. Whisk until smooth and well combined.
• Add the dry ingredients—1 cup all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 3/4 teaspoon cinnamon, 1/4 teaspoon ground nutmeg, and 1/4 teaspoon salt—to the wet mixture. Stir with a spatula or spoon until just combined; do not overmix.
• Pour the batter into the prepared pan and spread it into an even layer with a rubber spatula.
• Bake for 20–22 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs attached.
• Remove the pan from the oven and place it on a cooling rack. Let the bars cool completely in the pan before frosting.
• While the bars are cooling, make the frosting: in the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using an electric handheld mixer, beat 8 ounces very soft full-fat cream cheese, 2 tablespoons very soft unsalted butter, and 2 teaspoons pure vanilla extract on medium-high speed until completely smooth (about 2 minutes).
• Reduce the mixer speed to low and gradually add 2 cups sifted confectioners' sugar. After all the sugar is incorporated, beat on high speed for 1–2 minutes until the frosting is smooth and spreadable.
• Once the bars are completely cool, use the parchment overhang to lift them out of the pan and set them on a cutting board or serving tray. Gently spread the cream cheese frosting evenly over the top.
• Cut into squares and serve. Store the frosted bars covered in the refrigerator for up to 2 days.