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In a food processor, blend the biscuits with the butter and coconut to make the base for the pie. Press it into a deep 21cm fluted tart tin, going all the way up the sides and making sure the corners are not too thick.
In a large saucepan, melt both chocolates with the milk and cream over a very low heat, stirring slowly all the time. In a separate bowl, beat the egg yolks with the cornflour and sugar.
When the chocolate has melted, add the egg mixture and stir together until it thickens, about 10-12 mins. When the texture is like thick custard, pour it into the tin and even out the top using a spatula. Sprinkle with the hazelnuts and place in the fridge for at least 2 hrs.
Meanwhile, make the toffee sauce. Dissolve the sugar and 2 tbsp water in a large pan over a low heat. Bring to the boil and cook until golden and caramelised, about 2 mins. Whisk in the butter in small batches, then remove from the heat and stir through the cream. Set aside to cool.
To make the coffee cream, mix the coffee in 1 tsp boiling water to make a paste. In a large bowl, whip the cream halfway, then add the coffee, sugar and vanilla, and whip until soft peaks form. Cover and chill until ready to serve.
To serve, cut the pie into wedges. Reheat the toffee sauce in a small saucepan or the microwave and serve with the coffee cream.