Layered Terrine Gateau

For the cake: heat the oven to 190°C (170° fan) 375°F gas 5. Grease a 23cm x 30cm |9" x 13" Swiss roll tin and line with non-stick baking paper.

Place the sugar and eggs in a mixing bowl and whisk until very pale and light, using an electric whisk, until the beaters leave a trail on the surface.

Sift together the flour and cocoa powder and gently fold into the egg mixture.

Pour into the tin, tilting it so that it covers the whole surface. Bake for 12-15 minutes until firm and springy to the touch. Cool in the tin for 5 minutes, then place on a wire rack to cool completely and peel off the lining paper.

Cut the cake into 4 equal pieces.

For the filling: melt the chocolate in a heatproof bowl over a pan of simmering (not boiling) water.

Put the chocolate, chestnut puree, cream and vanilla into a food processor and blend until smooth. Put into a bowl and leave to stand for a few minutes until cooled and thickened. Stir in the candied chestnuts.

Sandwich the cake layers together with the chestnut cream.

For the covering: melt the chocolate as before, then remove from the heat and allow to cool slightly.

Sift the icing sugar into a bowl and beat in the butter until smooth and creamy. Add the cream and chocolate and beat well. Chill until firm and spreadable.

Spread the buttercream over the top and sides of the cake.