1. Preheat the oven to 200°C (180°C fan/400°F/Gas 6).
2. To make the filling, heat the oil in a frying pan. Add the onions and fry over a high heat for a few minutes. Cover, lower the heat, and cook for about 10 minutes until soft. Add the chestnuts, then increase the heat and fry for 2 minutes until toasted. Spoon into a bowl and leave to cool. Season with salt and freshly ground black pepper and add the cranberry sauce.
3. Cut the pastry into 24 x 10cm squares. Brush each square with melted butter. Put a small tablespoon of the filling into the centre of the square. Place one cube of cheese on top. Crunch the end to seal in the middle so it looks like a moneybag. Repeat with the remaining squares.
4. Place the canapés on a baking sheet lined with non-stick paper. Bake for about 15 minutes until golden and crisp. Serve warm.
IN THE AGA
Cook the parcels on the grid shelf on the floor of the roasting oven for about 10–12 minutes.
PREPARE AHEAD AND FREEZE
The parcels can be made and assembled up to 6 hours ahead. Freeze well uncooked for up to 1 month.