Preheat oven 180C.
Line a slice tin with baking paper and allow it to hang over the tin.
Sift flour and baking powder into a bowl.
Cut in butter until it resembles coarse breadcrumbs.
Mix in sugar and egg. Add sufficient milk to mix to a soft dough.
Knead until smooth.
Use 2 thirds to roll out to fit prepared tin base.
Use the other 1 third to roll out for the top.
Place base piece in tin and spread apple over it.
Lightly press top piece on top.
Bake for 25-30 minutes or until lightly browned.
Cool. Dust with sifted icing sugar. Cut into squares.