Line a baking sheet with greaseproof paper. Roll the pastry out on a lightly floured work surface and cut out four 10 x 12 cm (4 x 5 inch) rectangles. Place them on the baking sheet and sprinkle with the light brown sugar.
Arrange the apple slices in a line on each rectangle of pastry. Drizzle each one with the honey and then sprinkle over the grated Parmesan.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 12–14 minutes, until golden.
Meanwhile, to make the mascarpone cream, if using, whisk together the mascarpone, lemon rind and juice and muscovado sugar in a bowl.
Serve each tartlet with a dollop of mascarpone cream, if liked.