The Yule log, or is a French cake that represents the log burned in the hearth over Christmas. Pastry chefs can get very creative with these, and some versions are extravagant, complex and beautiful. This one is more home-style, and it's something children can help make, although be prepared for the mess.

Check the can of chestnut purée to make sure it's not sweetened. The type I buy (the Clement Faugier brand) comes in a 439-gram can.

Preheat the oven to 200 degrees Celsius. Spray a baking sheet (with dimensions of about 36cm x 28cm x 1cm deep) with pan coating then line it with baking paper.

Sift the flour with the cocoa powder. Break two of the eggs into a large mixing bowl. Separate the remaining two eggs, putting the yolks in the bowl with the other eggs, and the whites in a clean, dry mixing bowl.

Add 40 grams of sugar and the vanilla extract to the bowl containing the eggs and immediately start beating the ingredients with an electric mixer. Beat on medium speed until frothy, then turn the speed to high and beat until the mixture is thick and pale yellow. Turn off the mixer. Add the flour/cocoa powder to the bowl, put the mixer on low speed and stir until the flour/cocoa powder is just incorporated - do not overmix.

Wash the beaters from the mixer in hot, soapy water before drying them, then use them to whip the egg whites with the salt until frothy. With the mixer on medium speed, slowly add the remaining sugar. Turn the mixer to high and whip until the egg whites form soft peaks. Add about one-third of the whipped egg whites to the egg/flour mixture and use a rubber spatula to thoroughly combine the ingredients. Add half the remaining whites to the mixture and fold them in gently, trying to maintain as much volume as possible. Gently fold in the last of the whites. Spread the sponge mixture in an even layer into the prepared pan then bake at 200 degrees for about 10 minutes.

The cake is ready when it's fragrant, the surface is matte and firm to the touch, and it's pulling away from the sides of the baking tray.

Cool the cake completely, then quickly flip it over so it's paper side up on the baking tray. Peel off and discard the baking paper. Put a clean sheet of baking paper over the cake then put another baking tray (the same size as the sponge) over the baking paper so the cake is between two firm surfaces. Holding the two baking trays firmly, flip them over then lift away the top one - the cake will now be right side up.

Mix the chestnut purée with the brandy and a little cream to form a firm but malleable mixture. Spread the purée in an even layer over the chocolate sponge, leaving a 1cm border at the edges. Roll the cake lengthwise as tightly as possible. Wrap the roulade in a large sheet of parchment paper, then refrigerate it for several hours.

Preheat the oven to 95 degrees. Line an oven tray with baking paper.

Use an electric mixer to whip the egg whites on low speed until frothy. Add the salt and lemon juice, then, with the mixer on medium speed, add the sugar in a slow, steady stream. Turn the mixer speed to high and whip until the mixture forms medium peaks.

Put the meringue into a piping bag fitted with an 8mm plain tip. Make mushroom "caps" by piping small mounds (about 2cm in diameter) on the baking paper across half the tray, leaving a little space in between each one.

Across the second half of the tray, pipe the mushroom "stems" - squeeze out a blob about 1cm in diameter then lift the piping bag straight up so the meringue forms a cone with a pointed tip.

Bake the meringue mushrooms at 95 degrees for about two hours, or until they're completely dry. Turn off the oven and leave the mushrooms to cool until it's time to decorate the cake.

Tint the rolled icing with the green food colouring, roll it out to about 2mm thick on an icing sugar-dusted work surface, then use a holly leaf cutter or a knife to cut out leaves.

Heat the cream until simmering then pour it into a liquid measuring cup. Microwave the chocolate in a mixing bowl until it's 80 per cent melted, stirring every 30 seconds. Remove it from the microwave and stir, letting the residual heat melt it completely. Add the cream slowly into the chocolate, whisking constantly and letting each addition of cream incorporate fully before mixing in more. When it's ready, the ganache will be smooth and glossy.

Unwrap the cake roulade and spread some of the ganache over it to coat it completely then refrigerate until set.

Trim off the ends of the cake. Cutting on the diagonal, slice off two pieces from each end of the log (these will form the sawn-off "branches" of the tree). Put the log on a serving platter then place the two branches strategically on the log, using some ganache to help the pieces adhere. Spread another layer of ganache over the cake, leaving the ends exposed so you can see the spirals. Don't spread the ganache smoothly - it should look like tree bark. Chill the cake.

Use the tip of a paring knife to bore small holes in the bottom of the mushroom caps, then fit them onto the mushroom stems. Use a small sieve to lightly dust cocoa powder over the mushroom caps.

Place the mushrooms around the . Arrange the holly leaves and cranberries (to resemble holly berries) over the cake. Dust icing sugar over the cake, to resemble snow.