3 onions, peeled and finely sliced
6 sage leaves
4 tbsp olive oil
150²µ/5½´Ç³ú ²µ°ù³Ü²âè°ù±ð (or alternative vegetarian alpine cheese)
250g/9oz ready-rolled all-butter puff pastry
3 large cooked leftover roast potatoes (or boiled potatoes), quartered