- With the rack in the lowest position, preheat the oven to 200 °C (400 °F). Line a baking sheet with parchment paper.
- Core the apples and thinly slice with a mandolin.
- On a lightly floured work surface, shape the dough into a cylinder and cut into six discs. Roll out to about 3-mm (1/8-inch) thick, 14-cm (5 1/2-inch) circles. Cover the centre of each pastry with 15 ml (1 tablespoon) of chestnut purée or applesauce to about 2.5-cm (1-inch) of the border. Cover the purée with apples, making a centre of overlapping slices to form a rosette. Fold the edges of the dough inward, forming a crease.
- Place the tartlets on the baking sheet. Brush with the milk. Sprinkle with the sugar. Bake for about 35 minutes or until the tartlets are golden brown.
The flesh of Cortland apples doesn’t brown when baked and becomes slightly pink.