1 bunch watercress, leaves only
2 tbsp English mustard powder
salt and freshly ground black pepper
5 tbsp caster sugar
60g/2陆oz yellow mustard seeds
25g/1oz brown mustard seeds
2 tbsp olive oil
1陆 tbsp rapeseed oil
150ml/5f loz cider vinegar
2 tsp cider vinegar
110ml/4fl oz beer
陆 small wholegrain loaf, cut into 1.5cm/3in cubes