In a large bowl, mix the sherry, brandy, lemon juice and sugar until the sugar is dissolved. Stir in the cream, set the bowl over ice, and beat until thick enough to hold a soft peak, 4-5 minutes.
Spoon the syllabub into stemmed glasses and chill for at least 2 hours and up to 2 days. Sprinkle with ground nutmeg just before serving. Note On standing, syl