This classic Christmas dessert is a tradition in France. Evidently Napoleon believed cold air caused illnesses and ordered that all chimneys in Paris be closed in the winter. This eliminated the french tradition of gathering around an actual Yule Log on Christmas Eve, so in classic French fashion they developed a culinary confection to solve this problem and the tasty cake version of a piece of wood was invented.
These are a lot of fun to make, especially if you have some younger helpers to make the mushrooms. Though traditionally the mushrooms are made of meringue, this new and very simple technique it really fun to make. I like to also garnish the cake with fresh holly leaves. If you choose to use holly, avoid using any holly berries, they are slightly toxic. Instead, try using pomegranate arils for ruby red berries around the log.