Chock full of nutty flavor, these triple decker hazelnut brownies are sure to please all the chocolate + hazelnut lovers in your life.

Triple Decker Hazelnut Brownies

Hazelnut brownies are a delicious and nutty dessert or snack!

Course Dessert
Cuisine American
Prep Time 30 minutes
Cook Time 22 minutes
Cooling time 1 hour
Total Time 1 hour 52 minutes
Servings 16
Author Kelsie



  • 1/3 cup packed light brown sugar
  • 6 tablespoons unsalted butter at room temperature
  • 2/3 cup all-purpose flour sifted
  • 1/2 cup very finely chopped roasted hazelnuts

Brownie layer:

  • 2 ounces unsweetened chocolate finely chopped
  • 8 tablespoons unsalted butter
  • 2 large eggs
  • 1/2 cup granulated sugar
  • 1/2 cup packed light brown sugar
  • 1 teaspoon vanilla extract
  • 1/2 teaspoon espresso powder optional
  • 1/4 cup Frangelico can substitute Kahlua
  • 1/2 cup all-purpose flour sifted
  • 1/4 teaspoon salt
  • 1/2 cup chopped roasted hazelnuts


  • 6 tablespoons unsalted butter at room temperature
  • 2 cups powdered sugar sifted
  • 1 tablespoon Frangelico can substitute Kahlua
  • 1 tablespoon heavy cream or whole milk
  • 1/4 teaspoon salt


  • 2 ounces semi-sweet chocolate finely chopped
  • 1 ounce unsweetened chocolate finely chopped
  • 2 teaspoons refined coconut oil



  1. Preheat oven to 350 degrees. Spray a 9-inch square baking pan with cooking spray. Line the bottom with parchment paper and spray the paper. Set pan aside.
  2. Combine the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment. Cream on medium speed until light and fluffy. Gradually add the flour and mix until combined. Mix in hazelnuts until combined, then press into an even layer in the bottom of the prepared pan. (It will seem like there won’t be enough to cover the whole bottom; just keep going and you’ll get there.) Set aside.


  1. Combine the butter and chocolate in a microwave-safe bowl and heat in 30-second intervals, stirring after each interval, until chocolate is melted and mixture is smooth. Cool.
  2. Combine the eggs, sugars, vanilla, and espresso powder (if using) in a large mixing bowl. Whisk until blended. Stir in the cooled chocolate and Frangelico. Gradually whisk in the flour and salt, mixing until smooth. Fold in the hazelnuts. Pour filling over crust and smooth into an even layer with a rubber spatula. Bake for 22 to 25 minutes, until a cake tester inserted into the center comes out clean. (Don’t overbake them.) Cool completely on a wire rack before proceeding with the recipe.


  1. Place the butter in the bowl of a stand mixer fitted with the paddle attachment and mix until smooth. Add remaining ingredients and beat on medium speed until smooth and creamy. (If frosting is too thick, add additional Frangelico or milk to make it spreadable.) Spread over cooled brownies, then refrigerate for 30 minutes.


  1. Combine the chocolate and coconut oil in a small microwave-safe bowl. Heat in 15-second intervals, stirring after each interval, until chocolate is melted and mixture is smooth. Cool slightly, then spread over the frosting. Refrigerate until glaze is set, then slice into bars and serve. (Freeze leftovers, tightly wrapped, for up to 3 months.)