200g/7oz chestnut mushrooms, sliced
salt and freshly ground pepper
4 spring onions, thinly sliced
½ tsp Dijon mustard
40²µ/1½´Ç³ú plain flour
knob of unsalted butter
2 tbsp reduced-fat crème fraîche
1 large free-range egg, lightly beaten
160ml/5½fl oz milk