100g/3陆oz button mushrooms, diced as thinly as possible using a mandolin if possible
pinch English mustard powder
1 tbsp Worcestershire sauce
salt and freshly ground black pepper
oil, for frying
500g/1lb 2oz Hafod cheese, diced
1 free-range egg, plus 1 free-range egg yolk
50ml/2fl oz ale
4 slices sourdough bread