Hazelnut Meringue Layer Cake with French Coffee Buttercream and Caramelized Hazelnut Clusters
Serves: 10-16
For the meringue layers:
  • 220g (or 7.7 ounces) whole hazelnuts or hazelnut meal
  • 110g (or ½ cup + 2½ teaspoons) granulated sugar
  • 12g (or 4½ teaspoons) all-purpose flour
  • 5 large egg whites (175g, or 165ml, or ½ cup + 3 tablespoons)
  • 175g (or ¾ cup + 2 tablespoons) granulated sugar
For the caramelized hazelnut clusters:
  • 110g unsalted hazelnuts
  • 55g (or ¼ cup) unsalted butter
  • 100g (or ⅓ cup + 2 tablespoons, packed) light brown sugar
  • ⅛ teaspoon table salt
For the French coffee buttercream:
  • 2 teaspoons instant coffee granules
  • 1 tablespoon hot water
  • 200g (or 1 cup) granulated sugar
  • 5 tablespoons water
  • 10 large egg yolks (or 170g, about ⅔ cup)
  • 450g (or 2 cup) unsalted butter, softened at room temperature
  • 1 teaspoon vanilla extract
Start with the hazelnut meringue layers:
  1. Preheat the oven to 100°C/212°F (standard oven setting). Line two baking sheets with baking parchment. Using a cake pan or plate as a template, draw two 20-cm/8-inch circles on each sheet of baking parchment. Set aside.
  2. If using whole hazelnuts, place hazelnuts in a large ziplock bag, squeeze the air out of the bag and close it carefully. Place the bag on a chopping board and, using a rolling pin, crush the nuts into a fine meal, as fine as possible. Add the smashed nuts to the bowl of a food processor with the 110g of sugar and the flour and pulse until almost completely ground. It’s okay if there are still a few larger pieces of hazelnut in there. Set aside.
  3. In a large bowl, using an electric mixer set on high and fitted with the whisk attachment, beat the egg whites until foamy. With the mixer still running, add the 175g of sugar one tablespoon at a time. Once all the sugar has been added, keep mixing until the meringue looks glossy and smooth and holds stiff peaks, about 5-8 minutes. When you rub a bit of the meringue between your fingers, you should not be able to feel any sugar crystals.
  4. Using a rubber spatula, carefully fold the hazelnut-mixture into the meringue.
  5. Divide the mixture evenly between the prepared parchment circles. Place the baking sheets in the preheated oven and bake the meringue discs for 3 hours, or until completely dry and crisp. Halfway through baking, rotate the baking sheets between oven shelves to ensure even baking. When done, the discs can easily be removed from the baking parchment. Remove from the oven and allow the discs to cool completely.
  6. Discs can be made up to one day ahead and stored in an airtight container until needed.
Proceed with the caramelized hazelnut clusters:
  1. Preheat your oven to 160°C/325°F (standard oven setting).
  2. Place about 90g of the hazelnuts in a plastic sandwich bag and gently smash them with a rolling pin into smaller pieces the size of oat flakes. Add the reserved whole hazelnuts.
  3. In a small saucepan, combine the butter with the sugar and salt. Heat over low heat, stirring occasionally, until the butter has melted. Bring the mixture to a boil over medium-high heat and cook for 1 minute, stirring occasionally. Take the pan off the heat, add stir in the hazelnuts.
  4. Spread the hazelnuts onto a cookie sheet lined with baking parchment and bake for 10 minutes. After 10 minutes, give the nuts a good stir with a fork. The caramel will have melted around the nuts, but that’s fine. Just stir it all up to form clusters and leave the nuts to bake for 5 more minutes or until golden brown.
  5. Remove from the oven and stir the nuts again with a fork. Try to spread the mixture as evenly as possibly, to form bite size hazelnut clusters. Allow to cool completely.
  6. Can be made up to one week ahead and stored in an airtight container until needed.
Finally, make the French coffee buttercream:
  1. Dissolve the coffee in one tablespoon of hot water. Set aside to cool.
  2. Combine sugar and water in a medium-sized saucepan. Heat over low heat, stirring with a metal spoon until the sugar has dissolved and the syrup is clear. Crank up the heat to medium-high and allow syrup to come to a boil.
  3. In the meantime, place yolks in a medium-sized, heatproof bowl and mix (with an electric mixer fitted with the whisk attachment) until thick and foamy.
  4. Once the syrup has come to a boil, clip on a candy (or sugar) thermometer. Cook until the syrup reaches 114°C/238°F, then immediately remove from heat and slowly drizzle the hot syrup into the bowl with the yolks, mixing continuously to prevent the yolks from scrambling. Don't pour the syrup onto the whisk, or the syrup may splatter against the sides of the bowl (or into your face!). Instead, aim for a spot close to the whisk.
  5. Once all the syrup has been added, keep mixing until the bottom of the bowl feels cool to the touch and the pâte à bombe (aka: yolk meringue) has cooled down to room temperature.
  6. Once the pâte à bombe is cool, you can either incorporate the butter using the ‘beaten butter method’ or the ‘cubed butter method’ *. I prefer the beaten butter method.
  7. To incorporate the butter using the beaten butter method, beat the butter in another medium-sized bowl, using an electric mixer fitted with a whisk or paddle attachment, until pale and fluffy, about 2 minutes. Add the cooled pate au bombe one tablespoon at a time, mixing well after each addition. Once all the butter has been added, add the vanilla and the dissolved coffee and mix for another 5 minutes, or until the buttercream looks smooth and creamy.
To assemble:
  1. Place a dollop of buttercream on a serving plate and place one of the hazelnut-meringue discs on top. Using the back of a spoon, spread one fourth of the buttercream over the hazelnut layer, pushing it towards the edges of the disc. Top with another hazelnut-meringue disc. Repeat with the remaining buttercream and hazelnut-meringue layers, finishing with a layer of buttercream. Top with the caramelized hazelnut clusters. Serve immediately or within three hours. If you want to keep the cake for a longer time, store in an airtight container in the fridge and allow to come to room temperature before serving. This may take up to 4 hours. Cake is best served within two days after assembly.
* To incorporate the butter using the cubed butter method, start adding the butter one tablespoon at a time, mixing well after each addition. Once all the butter has been added, mix for another 5 minutes, or until the buttercream looks smooth and creamy. If the buttercream separates, just keep mixing like you mean business and the buttercream will come together again.
Recipe by The Tough Cookie at https://thetoughcookie.com/2015/09/04/hazelnut-meringue-layer-cake-with-french-coffee-buttercream-and-caramelized-hazelnut-clusters/