Prep: 35-40min (frosting) | Baking: 20min
(for a 4-layer cake using 17cm diameter tins)
For the cake:
100g butter, room temp
1 tsp baking powder
1 tsp vanilla sugar
1/8 tsp salt
1 tbsp milk
3 tbsp espresso
50g hazelnuts, blitzed
For the filling/ spread:
3-5 tbsp hazelnut spread
For the buttercream meringue:
1 egg white
1/4 cup granulated sugar
60g butter, chopped into 1 tbsp chunks and returned to the fridge
pinch of salt
1-2 tbsp espresso
Optional: Hazelnut croquant, ca. 3-4 tbsp
Wipe your hand whisk, electric whisk, and electric hand mixer (or standing mixer) utensils with lemon juice to ensure there is no grease. A single drop of grease or yolk will ensure the frosting never stiffens.
Bring a pot with ca. 1cm water to a simmer, and place the egg white and caster sugar in a glass or metal bowl over it, like you do when melting chocolate. Use the hand whisk to mix constantly until the sugar dissolves, and the mix is less goopy and more like sirup, 3min.
Remove the bowl from the heat, and use the electric hand mixer to whip the syrup into a meringue. It takes between 15-20min. I took a break 10min in, putting the bowl in the fridge for 5 min. My meringue had stiff peaks in the bowl, but on the mixer the peaks still curled down.
Halfway through mixing (while meringue is resting in fridge if doing that step), take the butter out of the fridge. Set aside as you return to mixing the meringue.
Once stiff (in the bowl), continue on with the electric hand mixer (if using a standing mixer, change from whisk to paddle attachment): Add the butter, one chunk at a time.
Lastly add the salt and coffee.
* If the buttercream becomes lumpy or curdled, set the bowl over a pot of simmering water and mix constantly until it returns to a smooth mixture.
Set buttercream frosting in the fridge until the cake layers have cooled from the oven.
Preheat oven to 180°C.
Beat butter, egg, sugar, vanilla, flour, milk, espresso, salt, and baking powder into a creamy mixture. Add hazelnuts and combine.
Spoon into layer cake tins, and bake 15 min.
Carefully remove layer cakes from their tins and place on a wire rack to cool.
Once cool, use 1-1.5tbsp hazelnut spread on 3 of the layer cakes as the 'glue' to keep the layers stacked. Press down gently as you stack each layer.
Spread the buttercream meringue frosting over the top of the cake (and the sides if desired).
Optional: sprinkle hazelnut croquant on top.