Photo: Laura Edwards
Preheat the oven to 180°C (160°C fan oven)/gas 4 and grease a 33 x 23cm rimmed baking tray (known as a quarter sheet pan) and line with a sheet of baking parchment. Grease the parchment and then dust with a little flour, tipping out any excess.
To make the sponge, put the eggs and sugar in a large bowl and, using an electric whisk, beat until pale and thick, so that when the beaters are lifted from the bowl the batter leaves a trail. Put the flour and cocoa powder in a bowl and mix together. In three additions, sift this mixture over the egg mixture, gently folding together with a spatula until fully combined. Pour this batter into the prepared baking tray and gently level out. Bake for 10–12 minutes until the cake springs back to the touch.
Meanwhile, put a tea towel on a work surface and cover with a piece of baking parchment. Remove the cake from the oven and immediately turn it out onto the parchment. Peel off the parchment from the base of the cake, and then carefully roll the cake tightly, with the parchment and tea towel inside. Leave to cool, wrapped inside the tea towel, for 20 minutes. This will help the cake to unroll and re-roll later without cracking.
Put the hazelnuts for the decoration on a baking tray and toast them in the oven for 10 minutes or until lightly browned. Set aside to cool.
To make the buttercream, melt the chocolate in a heatproof bowl over a pan of gently simmering water, making sure the base of the bowl doesn’t touch the water. Leave to cool slightly.
Meanwhile, put the sugar and 75ml water in a small pan over a medium-high heat and bring to the boil. When the sugar has dissolved, cook until the syrup reaches 120°C on an instant-read thermometer. When the syrup is around 115°C, put the egg and yolks in the bowl of an electric mixer fitted with the whisk attachment and whisk until pale and thickened (this is best done using a freestanding electric mixer). Once the syrup reaches 120°C, and with the mixer still running, carefully pour the syrup into the egg mixture. Continue whisking until the egg mixture has cooled to room temperature.
Add the butter, a few pieces at a time, beating until you have a silky smooth buttercream. Once all the butter has been added, add the praline paste and the melted milk chocolate, mixing to combine.
To make the syrup, put the sugar and 40ml water in a small pan and bring to the boil over a medium heat, then cook for 2 minutes. Remove the pan from the heat and pour in the Frangelico.
To assemble, unroll the sponge and remove the baking parchment, then brush liberally with the syrup. Spread three-quarters of the buttercream evenly across the sponge, then carefully roll it up tightly. Carefully lift the roll onto a serving plate and spread the remaining buttercream in a thin layer over the outside of the cake. To make the decoration, put the chopped hazelnuts in a small bowl and mix with the gold powder, if using. Press the nuts onto the buttercream, coating the cake.
The cake is best eaten on the day it is made, but it will still taste great up to two days later as long as it's kept in an airtight container. The buttercream can be made up to one week in advance. Store it in an airtight container in the fridge. Allow it to come to room temperature and beat it until light and fluffy before use.
This recipe is taken from Patisserie Made Simple by Edd Kimber (Kyle Books, £19.99)