1kg/2lb 4oz onions, finely sliced
1 tbsp plain flour
salt and black pepper
1.2 litres/2 pints stock (ideally beef but chicken or vegetable would also be fine)
50²µ/1¾´Ç³ú butter
150²µ/5½´Ç³ú ³Ò°ù³Ü²âè°ù±ð cheese, grated
1 baguette, cut into 1cm/½in slices