What is the name of the traditional French Christmas cake shaped like a log?

The traditional French Christmas cake shaped like a log is called a bûche de Noël.

The name means “Christmas log,” and the dessert is designed to resemble the large log once burned in the fireplace during the Christmas season. That older Yule-log custom was widespread in Europe, but the cake emerged as the firewood tradition declined. The dessert is generally associated with 19th-century France before spreading through other Francophone regions.

A classic bûche is made from genoise or another light sponge cake. The cake is baked in a shallow pan, spread with buttercream or another filling, rolled into a cylinder, and covered with icing. Chocolate buttercream is especially common, though coffee, chestnut, fruit, ganache, and liqueur-flavoured versions are also popular.

The log effect is usually created with fork marks in the icing, a cut end or branch-like piece, powdered sugar “snow,” and decorations such as meringue mushrooms. Stollen and panettone are also Christmas breads or cakes, but they are not rolled log-shaped French desserts.