First, the crust. Mix together the flour & icing sugar in a medium bowl. Add the butter & use your fingers to combine into crumbs. Add the lemon juice, egg, & water & carefully press/knead the dough together with your hands – if it seems too crumbly then add a little more water. When the dough holds together, wrap in cling film & refrigerate for 30 minutes.
Meanwhile, grease four 5.5-inch pie tins with a little butter & set aside. When ready, divide the dough into four equal sized balls. Individually roll the balls out on a lightly floured surface, & line each of the pie pans with ¾ of the ball, leaving the last ¼ behind for the top. Trim any excess away & add to the saved dough. Return the pie pans & the saved dough tops to the fridge to rest.
Now, the filling. In a large bowl, gently & thoroughly combine all of the ingredients. Divide the filling equally between the four chilled pie crusts & return to the fridge.
Preheat the oven to 200C. Cover a baking tray with baking parchment & set aside.
On a lightly floured surface, roll out each top crust dough just enough to cover the pies. Brush the edges of the ready made bases with the beaten egg & water mixture & place a top crust on each pie, gently pressing down the edges to seal shut. Brush the entire top of each pie with the egg mixture & sprinkle with some sugar.
Place the pies on the prepared baking tray & bake in the oven for 35-40 minutes, or until the crust is golden brown & the filling is fragrant & bubbling. Leave to cool slightly before enjoying with some lightly whipped cream!