Instructions

1. First make the filling:
2. Put the mushrooms into a food processor and blitz for a few seconds, until they are finely chopped.
3. Heat the butter in the oil, add the mushroom and cook until softened. Add the corn flour, salt& pepper, juice of half a lemon and the milk. Cook it for a couple of minutes or so, until creamy, then turn off the heat. Add the nutmeg, cream and crab, then combine gently - you should get a thick, creamy mixture. Taste it, then season with salt & pepper, lemon juice and Tabasco, to your taste. Set aside.
4. Preheat the oven to 200°C. Line a Swiss roll baking tray (30x20 cm) with parchment paper.
5. Rinse the spinach under cold water, then add to a pan of boiling, lightly salted water. Cook for a couple of minutes, until properly wilted, then rinse through a sieve under cold water. Squeeze the water out of the spinach using the back of a spoon.
6. Transfer the spinach to a food processor, add the butter and egg yolks. Pour the mixture into a big mixing bowl.
7. Whisk the egg whites into a hard (but not dry) foam with an electric whisk, then gently fold it into the spinach purée.
8. Tip the mixture into the lined baking tray and spread it out evenly, using a flat a flat wooden spoon. Sprinkle with Parmesan, if used.
9. Bake in the oven for 10 minutes.
10. Take it out of the oven and turn it out immediately onto a large sheet of grease paper, then carefully strip off the parchment paper from the other side.
11. Let it rest for a few minutes, then spread the filling evenly on the top, using a palette knife. Roll it up from the shortest end, using the paper to guide you (by pushing it away from you to make a tight roll). Sprinkle some more cheese on top if liked.
12. When the roulade is completely cooled, wrap it tightly in clingfilm and chill in the fridge until needed.
13. Cut it into 1-2cm thick slices just before serving.