Spread the apples and blueberries into an oven dish and mix with 2 tablespoons of caster sugar.
Roll the pastry over the top and cut around the edges. Use your thumb or a fork to press it down around the edges.
Beat an egg with 1 Tablespoon of caster sugar and brush it over the top of the pastry.
Put your pie into a pre-heated oven at around 180 Degrees for a fan oven and 200 for a conventional. Bake for 20 minutes or until the pastry is an even gold colour on top.