A pithivier is a French enclosed circular pie. It looks fancy, but with the saviour of shop-bought puff pastry it is relatively simple. You will only need the cylinder end of the squash for this ??? choose one with a diameter of roughly 8???10cm/3?????4 inches. Keep the rest of the squash wrapped in the fridge for up to a week, or cube and roast for tomorrow???s salad. Serve with steamed broccoli or a light green salad. You could replace the squash in this recipe with a similar sized disc of celeriac or beetroot wedges; use a total of 350g/12oz of vegetable across the two pies.