Old Fashioned Apple Pie Bars

Preheat oven to 400u0b0F. Grease an 8x12 inch rimmed baking tray and line base and long sides with parchment paper, extending paper 2 inches over sides.
Bring apples, 3/4 cup sugar and 1/2 cup water to a boil, covered. Reduce heat and simmer for 10 mins, or until apples are just tender. Transfer to a large colander or strainer to drain and let cool to room temperature.
To make the pastry dough, sift flour and powdered sugar into a large bowl. Cut in butter. Add egg and 1/2 cup milk and mix until combined. Transfer to a lightly floured work surface. Roll 2/3 of dough out and use to line base and sides of pan, with 1/3 inch extending over sides. Spread cold apple mixture over pie shell and brush edges with a little extra milk.
Roll out remaining dough until large enough to generously cover filling. Place over filling and press edges together to seal. Trim excess dough around edges then brush top with a little milk and sprinkle with remaining sugar. Slash about 6 holes in the pie lid and bake for 45 mins. Let cool in pan for 10 mins then transfer to a wire rack to cool.
Meanwhile, to make the passionfruit icing, sift powdered sugar into a medium heatproof bowl. Stir in passionfruit pulp to make a thick paste. Place bowl over a saucepan of simmering water and stir icing until spreadable. Spread icing over pie then cut into squares to serve.