Hazelnut Gateau

For the cake: heat the oven to 180°C (160° fan) 350°F gas 4. Grease a deep 23cm|9" springform cake tin and line the base with non-stick baking paper.

Melt the chocolate in a heatproof bowl over a pan of simmering (not boiling) water. Remove from the heat and set aside.

Beat together the butter and sugar in a mixing bowl until light. Beat in the egg yolks, one at a time until blended. Beat in the vanilla, salt and chocolate.

Whisk together the egg whites and salt until softly peaking. Stir half into the chocolate mixture, then fold in the remaining egg whites until just combined. Fold in the hazelnuts.

Pour into the tin and bake for 25-30 minutes until cooked through and springy to the touch. Cool in the tin for 5 minutes, then place on a wire rack to cool completely.

For the filling: beat together the butter and hazelnut spread until smooth and combined. Gradually sift in the icing sugar, beating until smooth. Beat in the cream.

Slice the cake in half horizontally. Invert one half and spread with the filling. Place the other cake on top.

Line a baking tray with non-stick baking paper.

Put the sugar and water into a heavy pan and heat gently until the sugar has dissolved completely.

Bring to a simmer, and cook for about 4 minutes, swirling the pan occasionally, until medium amber. Add the hazelnuts and stir for 1 minute to coat.

Pour onto the baking tray and immediately separate the nuts into clusters, using 2 forks. Leave to set, then break apart.

Whisk together the cream and icing sugar until thick. Spread over the top and sides of the cake.