"Making this cake is a process, but it pays off with a serious treat for chocolate-lovers. The cake layers are dense enough to hold up to the whipped fudge filling while still having a light, cakey texture, and the sweet milk chocolate in the buttercream is toned down with the addition of bittersweet chocolate. The whole cake is wrapped in a decorative chocolate-drizzle cage, but if you’re not feeling confident about pulling off that final flourish, just drizzle the melted chocolate over the top of the cake—I’m sure no one will complain. Game plan: You can prepare the cake layers up to a day in advance. Just wrap them tightly in plastic wrap and store at room temperature. The fudge filling and buttercream are best used right away. You can also prepare the entire cake up to 2 days in advance and refrigerate it. Just let it come up to room temperature for about 1 to 2 hours before serving. This recipe was featured as part of our birthday cake recipe gallery...."