This famous British dessert is a Christmas tradition, with its sherry-soaked sponge, red fruit and rich custard. If you prefer a non-alcoholic version, substitute orange juice for the sherry.
Preheat the oven to hot 220°C (425°F/Gas 7). Brush a 25 x 30 cm (10 x 12 inch) swiss roll tin with melted butter, line the base with baking paper and brush again with melted butter.
To make the sponge, bring a pan half full of water to the boil, then r