Nutella Crunch Layer
1/2 cup semisweet chocolate, finely chopped
1 tablespoon butter
1/2 cup plus 1 tablespoon Nutella
2 1/2 cups (7 5/8 ounces) feuilletine
1 15.25-ounce box chocolate cake mix
1 cup all-purpose flour
1 cup granulated sugar
1/4 cup plus 2 tablespoons unsweetened cocoa powder
3/4 teaspoon salt
3 large eggs
1 1/2 teaspoons vanilla extract
1/2 cup vegetable oil
1 1/3 cups water
1 cup sour cream
1 cup unsalted butter, room temperature
4 ounces cream cheese, softened
1 1/2 cups Nutella
1/2 cup plus 1 tablespoon (4 ounces) semisweet chocolate chips
1/2 cup plus 1 tablespoon (4 ounces) milk chocolate chips
1/2 cup confectioners' sugar
1/2 cup Nutella
- Make the Nutella Crunch Layer: Line an 8-inch cake pan with parchment paper then spray with nonstick cooking spray; set aside.
- In a large bowl, combine the chocolate chips and butter; melt over a double boiler set over hot water.
- Stir in the Nutella until well combined. Add in the feuilletine and gently stir into the Nutella mixture to coat.
- Transfer the mixture to the prepared pan and smooth into an even layer. Cover with plastic wrap then chill in the freezer until set and a firm layer, at least 30 minutes. Keep chilled until ready to assemble cake.
- Make the cake: Preheat oven to 350 degrees F.
- Line three 8-inch cake pans with parchment rounds and lightly spray with nonstick cooking spray.
- In a large bowl, whisk together the cake mix, flour, sugar, cocoa powder and salt until well combined.
- Add in the eggs, vanilla, oil, water and sour cream. Beat at low speed until all ingredients are combined, scraping down the sides of the bowl to keep even-textured. Beat for 1 minute longer.
- Divide batter equally between prepared cake pans. Bake for 20 to 25 minutes, or until a toothpick inserted near the centers comes out clean or with a few moist crumbs.
- Cool the cakes in the pans for 10 minutes then invert onto a plate, peel off the parchment paper and reinvert onto a wire rack to cool completely.
- Make the frosting: in the top half of a double boiler set over hot water, melt chocolates.
- In the bowl of a stand mixer fitted with the paddle attachment, beat the butter until smooth and creamy. Add in the cream cheese and beat until smooth and well combined, about 1 minute.
- Add in the Nutella and mix until completely incorporated. Add in the melted chocolate and mix until well combined. Cover with plastic wrap and keep in a cool place until ready to use.
- Assemble the cake: take the Nutella crunch layer out of the freezer, remove plastic wrap and parchment and place in the middle of a cake board or large cake plate.
- Frost the crunch layer with a thin layer of the 1/2 cup Nutella.
- Place the first cake layer over crunch later. Top with 1/2 cup of the Nutella frosting.
- Repeat with remaining layers. Frost entire cake with remaining Nutella frosting.