Banana Bread Brownies with Brown Butter Frosting

Ingredients

Bananas: Use 1½ cups mashed very ripe bananas, approximately 3–4 medium bananas. Measure after mashing for consistent results.

Butter: Prepare ½ cup softened unsalted butter for the batter and another ½ cup for the brown butter frosting.

Sugar: Use 1 cup granulated sugar and ½ cup packed light brown sugar for a sweet, moist banana base.

Eggs: You need 2 large eggs at room temperature so they blend easily into the batter.

Sour cream: Measure 1 cup full-fat sour cream to give the bars a tender texture.

Vanilla: Use 2 teaspoons vanilla extract in the batter and 1 teaspoon in the frosting.

Flour: Measure 2 cups all-purpose flour, spooned into the measuring cup and leveled.

Baking soda and salt: Prepare 1 teaspoon baking soda and ½ teaspoon salt.

Frosting ingredients: Along with the reserved butter and vanilla, you need 3 cups powdered sugar and 3–5 tablespoons milk.

Optional walnuts: Add ½ cup chopped walnuts for crunch, or leave them out for smooth, tender banana bars.

Instructions

Preheat the oven: Set the oven to 350°F (175°C). Position a rack in the center.

Prepare the pan: Grease a 9×13-inch baking pan and line it with parchment paper, leaving an overhang for lifting.

Mash the bananas: Mash the peeled bananas with a fork until mostly smooth. A few small pieces are fine.

Cream the butter and sugars: Beat the softened butter, granulated sugar, and brown sugar for 2–3 minutes until light and creamy.

Add the eggs: Beat in the eggs one at a time, scraping down the bowl after each addition.

Mix in the wet ingredients: Add the sour cream, mashed bananas, and 2 teaspoons vanilla. Mix until combined; slight curdling is normal.

Combine the dry ingredients: In a separate bowl, whisk together the flour, baking soda, and salt.

Make the batter: Fold the dry ingredients into the banana mixture just until no dry flour remains. Avoid overmixing.

Add optional walnuts: If using, gently fold the chopped walnuts into the batter until evenly distributed.

Fill the pan: Spread the batter evenly into the prepared pan, smoothing the surface with a spatula.

Bake the bars: Bake for 30–38 minutes, checking at 30 minutes. A toothpick inserted into the center should come out clean or with a few moist crumbs.

Cool slightly: Place the pan on a wire rack and let the bars cool for about 20–30 minutes before frosting.

Brown the butter: Melt the reserved ½ cup butter in a light-colored saucepan over medium heat, stirring frequently.

Watch for golden flecks: Continue cooking until the milk solids turn golden brown and smell nutty. Immediately pour into a heatproof bowl, including the brown flecks.

Prepare the frosting: Whisk in the powdered sugar, remaining vanilla, and 3 tablespoons milk. Add more milk, a teaspoon at a time, until thick but spreadable.

Frost the bars: Spread the frosting over the slightly warm bars. It sets quickly, so work promptly and gently.

Cool and slice: Let the frosted bars cool completely before lifting from the pan and cutting into 20 squares.

Variation

Chocolate chip banana brownies: Fold ¾ cup semisweet chocolate chips into the batter instead of the optional walnuts.

Cinnamon banana bars: Add 1 teaspoon ground cinnamon to the dry ingredients for a warm spice flavor.

Pecan banana brownies: Replace the optional walnuts with an equal amount of chopped pecans. Toast and cool them first for extra flavor.

Maple frosting: Replace 1 tablespoon of the frosting milk with pure maple syrup, then adjust the remaining milk as needed.

Storage

Room temperature: Keep the frosted bars in an airtight container in a cool room for up to 2 days.

Refrigeration: For longer storage, refrigerate for up to 5 days. Let individual portions sit at room temperature briefly before serving.

Freezing: Freeze individual squares until firm, then wrap tightly and place in a freezer container for up to 2 months.

Thawing: Thaw wrapped bars overnight in the refrigerator. Unwrap after thawing to help keep condensation off the frosting.