Melt the butter in a saucepan. Add the onions and pumpkin and cook, stirring occasionally, for 5 minutes.

Gradually stir in the stock, salt, celery, potato, lemon juice, Tabasco and paprika, and bring to the boil. Reduce the heat to low, cover and simmer for 30 to 35 minutes, or until the pumpkin and vegetables are cooked and tender.

Remove the pan from the heat and pour the soup through a strainer into a bowl, pressing down on the pulp with the back of a wooden spoon to extract all the juices.

Discard the pulp. Stir the cream into the soup and return to a saucepan. Heat, stirring constantly, for 5 to 6 minutes, or until the soup is very hot but not boiling.

Serve at once.