Preheat the oven to 200°C (fan-assist). Cut the puff pastry into 8 squares. Wash, core and finely slice the apples. The best variety of apples for the filling is South Tyrolean Braeburn PGI. Slice the camembert. Dust the puff pastry with flour and straighten out, with the two corners to the left and the right. Place a piece of camembert lengthwise in the centre of the pastry, and top with a slice of apple. Slice the onions finely, arrange on top of the apple and brush lightly with olive oil. Combine the herbs and sprinkle over the squares. Fold the corners over and press gently to seal. Whisk the egg yolk and milk together, brush the pastry and sprinkle with parmesan. Bake for 15-18 minutes until golden brown.