This is a take on the French gateau Pithivier, which is filled with a delicious almondy paste and rarely seen on menus these days. It's not really a gateau but a pie and I've bastardised it into a savoury version. The cheese you use is up to you, but a hard cheese like cheddar or Lancashire or Emmenthal works very well. You can serve this as a snack or as a vegetarian main course or starter.
2 x circles of butter puff pastry about 30cm diameter and rolled to about 2-3cm thick
500g large potatoes, peeled and cut into slices about one-third of a centimetre thick
litre chicken or vegetable stock
250g mature hard cheese, grated
1 medium onion, peeled, halved and finely chopped
Salt and freshly ground black pepper
1 medium egg, beaten
Preheat the oven to 200C/gas mark 6. Bring the stock to the boil, add the potatoes and simmer for 2 minutes, then drain in a colander over a bowl, reserving the stock for another time.
Place one of the circles of pastry on a baking sheet and prick it all over with a fork.
Lay one circle of the pastry on a baking sheet, then put a layer of the potatoes on the pastry about 3cm within the edge, season and scatter the cheese and onion on top.
Repeat until all of the potatoes have been used.
Brush the edge with a little egg and lay the other circle on top, stretching it a little over the potatoes and pressing the two edges together with your thumb.
Mark the edge of the pastry with the back of a knife and, if you wish, score the pastry lightly on the surface from the centre to the edge in curved lines about 1cm apart; then leave in the fridge to rest for an hour.
Brush the top with egg and bake for about 30-40 minutes until golden then remove from the oven.
Serve hot or at room temperature.