Peel lemons very thinly and put rind (which must be quite free of bitter white part) to soak in sherry for at least 12 hours.
Then take out lemon peel.
Add brandy, cream, egg white, sugar and freshly squeezed lemon juice.
Whip mixture until cream becomes fairly frothy.
Pour into syllabub glasses.
Refrigerate at least 6 hours before serving.