Combine apples, butter, sugar and cinnamon and cook on low flame till the apples become soft but still holds shape.
Squeeze in the lime juice and allow to cool completely.
Thaw puff pastry as per pack instruction.
Preheat oven to 180 degrees. Line a baking tray with parchment paper.
On a floured surface, flatten up the puff pastry and cut into four squares. Spoon in some of the apple mixture and fold the pastry, closing at the edges tightly.
Transfer to the baking tray, brush well with milk.
Bake for 30 minutes or till golden brown. Have warm.
Make sure that the filling is not too fluidy. Use hard apples for this purpose. This dessert is mildly sweet. You may dust with icing sugar before serving. If you like a darker top, pass it through the grill option till it browns.