green beans or green salad, to serve
1 large onion, sliced
600g/1lb 5oz potatoes, peeled
260g/9½ oz spinach, washed
½–1 tsp English or Dijon mustard
salt and freshly ground black pepper
25g/1oz butter
50²µ/1¾´Ç³ú butter, melted
175g/6oz mature or vintage cheddar, coarsely grated
175ml/6fl oz double cream
1 large egg or 2 medium, beaten
7–8 filo pastry sheets