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Close-up of fudgy peanut butter brownies topped with creamy frosting and chocolate drizzle on a wooden board.

Decadent Chocolate Zucchini Brownies with Creamy Peanut Butter Frosting

These fudgy chocolate zucchini brownies are incredibly moist and secretly packed with vegetables, topped with a rich, sweet, and salty peanut butter frosting for an irresistible treat.
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Prep Time 25 minutes
Cook Time 30 minutes
Total Time 55 minutes
Servings: 16 pieces
Course: Dessert
Cuisine: American
Calories: 350
Ingredients Equipment Method Notes

Ingredients
  

For the Chocolate Zucchini Brownies
  • 1 1/2 cups All-purpose flour
  • 3/4 cup Unsweetened cocoa powder
  • 1 tsp Baking powder
  • 1/2 tsp Baking soda
  • 1/2 tsp Salt
  • 1 1/2 cups Granulated sugar
  • 2 large Eggs room temperature
  • 1/2 cup Vegetable oil
  • 1 tsp Vanilla extract
  • 1/4 cup Milk
  • 2 cups Shredded zucchini firmly packed, excess moisture squeezed out
  • 1 cup Semi-sweet chocolate chips
For the Peanut Butter Frosting
  • 1/2 cup Unsalted butter 1 stick, softened
  • 1 cup Creamy peanut butter
  • 2-3 cups Powdered sugar sifted, adjust to desired consistency and sweetness
  • 2-4 tbsp Milk as needed for consistency
  • 1 tsp Vanilla extract
  • 1/4 tsp Salt

Equipment

  • 9x13 inch baking pan
  • Large mixing bowl
  • Medium mixing bowl
  • Whisk
  • Rubber Spatula
  • Electric mixer (handheld or stand)
  • Box grater or food processor
  • Measuring cups and spoons

Method
 

For the Chocolate Zucchini Brownies
  1. Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan, or line with parchment paper, leaving an overhang on the sides for easy lifting.
  2. In a large bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt. Set aside.
  3. In a separate medium bowl, whisk together the granulated sugar, eggs, vegetable oil, vanilla extract, and milk until well combined.
  4. Add the wet ingredients to the dry ingredients and mix with a rubber spatula until just combined. Be careful not to overmix.
  5. Gently fold in the shredded zucchini and chocolate chips until evenly distributed throughout the batter.
  6. Pour the brownie batter into the prepared baking pan and spread evenly.
  7. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, but not wet batter. Do not overbake.
  8. Let the brownies cool completely in the pan on a wire rack before frosting, about 1-2 hours.
For the Peanut Butter Frosting
  1. In a large bowl, using an electric mixer, cream together the softened unsalted butter and creamy peanut butter until light and fluffy, about 2-3 minutes.
  2. Gradually add the sifted powdered sugar, 1 cup at a time, mixing on low speed until combined, then increasing to medium.
  3. Add the vanilla extract and salt. Slowly add the milk, 1 tablespoon at a time, until the frosting reaches a smooth, spreadable consistency. You may not need all of the milk.
  4. Beat on medium-high speed for another 1-2 minutes until light and fluffy.
Assembly
  1. Once the brownies are completely cooled, spread the peanut butter frosting evenly over the top using an offset spatula or the back of a spoon.
  2. Cut into squares and serve.

Notes

To squeeze excess moisture from zucchini, place shredded zucchini in a clean kitchen towel or paper towels and wring out as much liquid as possible. This prevents soggy brownies. Store leftover brownies in an airtight container at room temperature for up to 3 days, or in the refrigerator for up to 5 days.