We get a little weak-kneed with delight around cakes, particularly cakes whimsically shaped to look like something else—in this case, a Yule log. Made famous in France as Bûches de Noël, these sheet cakes, filled, rolled, and frosted to look like the trunks of trees, complete with the stumps of sawed off branches, provide creative cooks the very real opportunity to play with their food. Want a few woodsy meringue mushrooms made from meringue to continue the conceit? Why not?