Bûche de Noël, chocolate and orange log

French pâtisserie windows are a delight at any time of the year, but by the middle of December they are filled with beautifully decorated bûches de Noël, which always inspire me. The cake part is not difficult to make; the skill and creativity lies in the decorating. One year I offered to make the dessert for a Christmas party and chose to make a large chocolate bûche. I made four Swiss rolls, cutting one of them into angled pieces, so that I could join the rolls other