Mary Berry has shared her 'foolproof' recipe for a classic Christmas dessert. The TV cook and author says her yule log, or Bûche de Noël, is "utterly delicious" and only takes an hour to make.

Start by preheating the oven to 200C/180C Fan/Gas 6. Lightly grease a 33x23cm/13x9in Swiss roll tin and line with baking paper, pushing it into the corners. For the sponge - in a large bowl, whisk the four eggs and 100g of sugar using an electric hand whisk until the mixture is pale and frothy. Sift 65g of self-raising flour and 40g of cocoapowder into the bowl and fold them in using a spatula until incorporated. Be careful not to beat any of the air out of the mixture. You are looking for uniform colour and a 'ribbon' texture, where the batter leaves a 'ribbon-like' trail that briefly holds its shape. Gently pour the mixture into the lined tin and spread evenly into the corners. Bake in the middle of the oven for eight to 10 minutes, or until well risen and firm to the touch, and the sides are shrinking away from the edge of the tin. While the cake is still hot, cut a piece of baking paper bigger than the Swiss roll tin and place it on the work surface. Dust generously with icing sugar. Carefully turn out the cakeonto the paper and remove the bottom lining paper.

To help you roll up the sponge tightly, cut a score mark parallel to one of the longer edges - about 2.5cm/1in from the edge and only cutting about halfway through the cake.

Starting with this edge, begin to tightly roll up the sponge and the paper. Roll with the paper inside and sit the roll on top of its outside edge to cool completely. Don't worry if the sponge cracks a little as you reroll it - it will be covered later.

While the cake is cooling, make the ganache topping. Heat 300ml of cream in a pan until it is very warm, but not so hot that you can't touch it. It only needs to be hot enough to melt the chocolate. As Mary says: "Remember that chocolate will melt in a child's pocket".

Remove from the heat and add 300g of chocolate, stirring until it is melted. If the cream is too hot, there's a greater risk of the chocolate seizing or losing its gloss.

Cool to room temperature, then place in the fridge or a cold location to firm up. This icing needs to be very thick for piping, but keep an eye on it as you don't want it to set too firm.

Unroll the cold sponge and remove the paper covering it. Spread 300ml of whipped cream evenly across the entire surface of the cake and roll tightly.

Cut a quarter of the cake off from the end on the diagonal. Transfer the large piece of cake to a serving plate and angle the cut end into the middle of the large cake to make a branch.

Put the chocolate icing into a piping bag fitted with a star nozzle. Pipe long, thick lines along the cake, covering it completely so that it resembles the bark of a tree.

Cover each end with a swirl of icing or, if you wish to see the cream, leave un-iced. Alternatively, just use a palette knife to spread the icing and create rough bark texture with a fork.

Dust with icing sugar and garnish with fresh holly or a little robin to serve. The cake will only keep for a few days and should be stored in the fridge if made in advance.