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To make the pastry, rub the butter into the flour, work in egg and water, and knead lightly. Use half to line a 10-inch metal flan dish.
Remove the coarse stalks of the greens, shred leaves thinly, mix with other ingredients (I also added black pepper) and pack into the dish.
Cover with pastry, keeping some back to make decorations for the top.
Bake at 150°C for 50 mins (mine took an hour), brushing the top with a little butter and sprinkling on a little fine sugar before serving.