Don't show your partner or kids before they're ready, otherwise they will eat all the ingredients before the tarts are ready!
Unroll the shortcrust pastry sheet and cut into 4 equal rectangles and place onto a baking tray.
Dice the apples into small cubes and scatter evenly over the pastry rectangles, along with 4-6 blackberries, leaving a border to allow the pastry to rise.
Brush the pastry borders with beaten egg or milk and then pinch up the pastry to create a wall around the tart. Sprinkle with a little demerara sugar and bake for 15-20 minutes or until golden brown.
Once cooked sprinkle a little demerara sugar to finish.
Use a baking tin and parchment paper to save washing up!