Not only fun for children to help make, this traditional French Christmas cake is perfect for an indulgent tea time, and the adults won’t be able to resist either.
Preheat the oven to very hot 230°C (450°F/Gas 8). Line a 25 x 30 cm (10 x 12 inch) swiss roll tin with baking paper. Bring a pan half full of water to the boil, then remove from the heat. Have ready a heatproof bowl that fits over the pan without touching the wa