Mix flour, icing sugar, and cocoa powder in a bowl while beating the egg, lemon juice, and 30ml water separately.
Rub the butter into the flour mixture until it resembles fine breadcrumbs, then incorporate the egg mixture by hand.
Form the dough into a ball, knead lightly on a floured surface until smooth, and chill for 30 minutes.
Preheat the oven to 190°C and heat a heavy baking tray.
Roll out the pastry, line a 25cm tin, prick the base, and chill for 10 minutes.
Bake blind with paper and beans for 15 minutes, remove weights, then bake for 12 minutes at 180°C.
Melt chocolate and butter over simmering water and let cool slightly.
Boil sugar and golden syrup in a saucepan then cool to room temperature.
Stir the chocolate, syrup, vanilla, and pecans into the beaten eggs.
Pour filling into the crust and bake for 30 to 40 minutes until set.