Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4. Grease and line two 20cm loose-bottomed round cake tins.
2. For the hazelnut cakes, spread out the hazelnuts in a shallow roasting tin. Bake in the oven for 8-10 minutes until lightly toasted, golden brown and fragrant. Watch carefully so they don't burn. Leave to cool slightly.
3. Cream the butter and sugar together with a free-standing mixer or a hand mixer until light and fluffy then add the eggs and flour. Beat again until well mixed.
4. In a food processor blitz 100g of the toasted hazelnuts until finely ground (they should resemble a sandy consistency). Fold into the cake batter then divide between the two tins. Spread level and put in the oven to bake for 30-35 minutes until golden brown and springy to touch. To check they are cooked, insert a skewer into the middle of each cake, it should come out clean. Leave to cool in the tins for 15 minutes before turning out onto a cooling rack.
5. Once the hazelnut cakes are turned out, wash the cake tins and grease and line as before, ready for the chocolate cakes.
6. Next make the chocolate cake mixture. Break up the dark chocolate into a large heatproof bowl. Pour 175ml boiling water on top and whisk to combine. Once fully melted add the cocoa, butter and sugar. Beat until smooth. Add all the remaining ingredients and mix with a balloon whisk to get rid of any lumps and beat again until smooth. Pour into two cake tins and bake for 30-35 minutes. Set aside to cool in the tins for 20 minutes before turning out onto a cooling rack to cool completely.
7. For the buttercream icing, in a free-standing mixer or using an electric hand whisk, beat the butter with half of the icing sugar. Beat until ice white, around 5 minutes.
8. Add the remaining sugar and beat for a further 3 minutes until fully incorporated and smooth. Remove about one third of the buttercream to a separate bowl – this will be used to sandwich the cakes together. Set aside the rest to ice the outside and top of the cake.
9. When all the cake layers are completely cold, you can begin to assemble the cake. Gently warm the caramel sauce in a small saucepan over a low heat, until it loosens and becomes easier to spread – its important that it doesn't get too warm. Put one of the chocolate sponges on a cake plate. Using the buttercream set aside for the filling, spread about a third of this on top then drizzle with 50g of the caramel over the top.
10. Top with one of the hazelnut cakes and repeat with the buttercream and caramel. Continue to layer the cakes alternately, sandwiching them together as before.
11. Before fully icing the cake, do a crumb coat – this provides a smoother base for the icing and will give a neater finish. To do this, use a palette knife to spread a very thin layer of the buttercream around the sides and top of the cake, ensuring the whole cake is covered. Put in the fridge for 30-40 minutes to firm up.
12. Finally, fully ice the cake with the remaining buttercream, making sure it is evenly spread to create straight, smooth sides.
13. Drizzle the remaining caramel around the top of the cake so that it drips down the sides.
14. Roughly chop the remaining toasted hazelnuts, then scatter these on top of the cake. Decorate the top of the cake with purple Quality Street. If you like, add some sparklers to the top of the cake and light them just before serving.
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    Quality Street cake