1. Preheat the oven to 200C/400F/gas mark 6. Roll out the pastry to a thickness of about 5mm. Cut out circles about 12cm in diameter and place on a baking sheet.
2. Peel, core and slice the apples. Place the slices in a bowl and squeeze over the lemon juice.
3. Carefully brush the outside rim of the pastry with the beaten egg, taking care not to let the egg drip down the sides (this prevents the pastry from rising evenly). Fan out the apple slices on the surface of the pastry, leaving a narrow rim around the edge.
4. Mix together the sugar and cinnamon in a small bowl and sprinkle over the apples. Bake for 1012 minutes until risen and golden.
5. While the tarts are baking, whisk the whipping cream until it begins to thicken, then add the Calvados, depending on desired strength, and continue to whisk until it just holds its shape.
6. Serve the tarts warm with a dollop of cream on the side and garnished with a mint sprig and berries, if desired.
Tip: Buy already rolled puff pastry to make this an even easier and quicker dessert. If you dont have Calvados, regular brandy will do.