Heat a large frying pan until medium hot. Add the butter, shallot and curry powder and fry for 2-3 minutes, or until just softened.
Add the sweetcorn and then pour in the wine and enough water to just cover.
Bring to a simmer, add half of the cream and then season with salt and black pepper.
Bring the mixture back to the boil, remove from the heat to cool slightly and then transfer to a blender. Bend until very smooth and light, for a good 5 mins then return the soup to the pan to heat though.
Make some soured cream by whisking the remaining cream with the lemon juice until thickened. It takes a while but is well worth it!
Ladle the soup into a serving bowl and then sprinkle with a little of the crab and add a spoonful of the now firm soured cream in the middle.
Enjoy how wonderfully light, tasty and warming this soup is!