This is a great celebration cake when you feel like making a little extra effort. Coffee and chocolate give it a chic, grown-up feel.
Preheat the oven to gas 150c. Place the egg whites in a large mixing bowl and whisk until soft peak. Add the sugar a little at a time whisking continuously until stiff and glossy then fold in the vinegar, cocoa and cornflour. Spread the meringue mixture into a swiss-roll tin lined with baking parchment and cook for approximately 1 hour. Remove from the oven and cool in the tin slightly before turning out and cutting into 3 even strips.
To make the filling, mix the coffee and chestnut puree in a bowl until smooth and add the cream. Beat until fairly thick but be careful not to let the cream split. To assemble the cake, lay one strip of meringue on a serving platter and dollop over one half of the coffee cream. Top with another strip of meringue and add the rest of the cream. Finish with the remaining strip of meringue. Place in the fridge or freezer for 1 hour to set, slice and serve. You can always dust the top of the cake with icing sugar, cocoa powder or grated chocolate for extra wickedness.
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