Grease a 25cm tart tin. For the
pastry, sift the flour, cocoa powder, icing sugar and salt into a bowl.
Set aside.
Melt the butter and water over a low
heat. Pour over the flour mixture and stir until the dough is smooth.
Press the dough evenly over the base
and side of the tart tin. Chill while preparing the filling.
Preheat a baking sheet in the oven at
190oC/375oF/Gas 5. Whisk the sugar and eggs until
the sugar is dissolved. Add the lemon rind and juice and mix well. Add
the cream.
Pour the filling into the pastry case
and bake on the hot baking sheet until the filling is set, 20-25
minutes. Cool on a wire rack, then decorate with chocolate curls.