To make the choux pastry, put the butter and 200ml (7fl oz) of water in a pan and bring to the boil. When boiling hard, turn off the heat and add the flour. Beat to a paste, until it comes away from the edges of the pan. Remove and let cool for 10 minutes.
Meanwhile, line a baking sheet with nonstick baking paper. Return the cooled paste to the pan and beat in the eggs, 1 tbsp at a time, and a pinch of salt. When smooth, put the paste in a piping bag with a plain nozzle, and pipe out 24 walnut-sized choux balls.
Preheat the oven to gas 6, 200°C, fan 180°C. Bake for 25-30 minutes until golden brown. Remove from the oven and skewer a small hole in the bottom of each bun. Leave to cool.
For the filling, put the lemon zest and milk in a pan. Bring to the boil, then set aside for 10 minutes. In a bowl, whisk the egg yolks and sugar until pale and light, then fold in the flour and cornflour. Slowly pour the cooled milk into the mixture, while whisking. Return to the pan and warm over a low heat until thickened, then sieve to remove the zest. Cover with clingfilm and leave to cool.
Add the mascarpone to the mixture and beat until smooth. Spoon into a piping bag with a narrow nozzle and fill each pastry bun with the cream.
To assemble, heat the chocolate in a microwave for 1 minute until just melted. Dip the base of 7 buns into the melted chocolate and arrange in a circle on a serving dish. Using the same technique to fix them, pile the rest
of the buns into a pyramid. Drizzle the remaining sauce over the pyramid. Place in the fridge to set for at least 1 hour. Serve decorated with redcurrants, if you like.
This recipe is best served with fresh redcurrants.
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