Preheat the oven to 220C/425F/Gas 7.
Gently melt the butter in a pan and sauté the apple with the dates and maple syrup for a few minutes.
Lay the ready-made filo pastry sheet flat on a clean surface. Place the mixture on top and fold over to make a triangle. Seal the edges with the beaten egg and dust generously with icing sugar.
Place on a non-stick baking tray and bake in the oven for 5-6 minutes, or until golden.
To make the crème anglaise, whisk the sugar and egg yolks in a bowl until pale and fluffy.
Gently heat the milk and cream in a pan until nearly boiling. Pour the hot milk mixture onto the egg mixture, and keep whisking constantly to avoid curdling. Return to the pan and stir until thickened.
Remove the apple parcel from the oven and transfer to a serving plate.
Drizzle the crème anglaise over to serve.