Pre-heat the oven to 200 ºC. On a floured surface, roll out the puff pastry. With a rolling pin, roll it until it’s about 3mm thick. Cut into a neat rectangle. Cut around 4 strips of 5mm wide. Place the dough rectangle on a greased baking tin.
Paint the edges of the dough strips with water and arrange all around the edges of the rectangle. Beat the butter and sugar until light and creamy. Add the egg and beat for another minute. Add the almonds and flour. Mix well.
Spoon the filling onto the crust and spread evenly. Cut the apples in half and then into thin slices. Arrange on top of the filling, making sure to cover it completely.
Bake for 30 to 35 minutes or until golden brown. Serve with ice cream or thick creanm.