Boil the coffee in a saucepan to reduce it by half and leave to cool. In a heatproof bowl over a pan of simmering water melt the chocolate and butter, stirring gently until the chocolate is completely melted.
Take off the heat and add the coffee reduction stirring continuously until cooled slightly. Add the egg yolks and stir until smooth.
In a separate bowl, whisk the egg whites until they form soft peaks, then whisk in the sugar. Stir a quarter of the egg whites into the chocolate to lighten the mix, then fold this mixture into the remaining egg whites using a metal spoon, followed by the whipped cream.
Gently fold in walnuts and pour into serving glasses, refrigerate for one hour before serving, topped with cream and dusted with cocoa powder with dipped strawberries.
For the dipped strawberries:
Break the chocolate into pieces then roughly chop. Melt in a heatproof bowl set over a pan of simmering water. Add 50g butter and stir until melted, then gently stir in the double cream.
Wash the strawberries and leave the stalk on, dip into the chocolate and place on a greased plate, put in the fridge for at least one hour.
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