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)
50驳/1戮辞锄 butter
150驳/5陆辞锄 骋谤耻测猫谤别 cheese, grated
1 baguette, cut into 1cm/陆in slices