200g/7oz chestnut mushrooms, sliced
salt and freshly ground pepper
4 spring onions, thinly sliced
陆 tsp Dijon mustard
40驳/1陆辞锄 plain flour
knob of unsalted butter
2 tbsp reduced-fat cr猫me fra卯che
1 large free-range egg, lightly beaten
160ml/5陆fl oz milk