Inspired by an eGullet demo, I thought I would try my hand at making a Bûche de Noël (Yule Log). I used a recipe from The Cake Bible by Rose Levy Berenbaum for the cake and the filling came from the Strawberry Cream Cake recipe of Cook's Illustrated (except I added Kahlua). I even went the extra mile and made meringue mushrooms. They were really easy and so impressive. The entire thing went so smoothly I could hardly believe it. I only had to swear once, when I was rolling the cake (it cracked).
The cake part is a chocolate sponge cake, which means that whipped egg whites provide all of the leavening - there is no baking soda or powder. Rose's recipe is almost a souffle since there isn't any flour, either. Next time I'll use a more traditional Swiss Roll recipe but I hadn't tried Rose's so I thought I would give it a whirl.
Most recipes instruct you to roll up the cake while warm and then unroll, spread on the filling, and re-roll when cooled. Rose says to just cool it in the pan and then fill and roll it. I was skeptical, but followed the instructions (for once). I should have followed my gut, since the thing cracked nearly to pieces when I was rolling up the log. Rose states that having a lower amount of sugar than is typical of a sponge cake keeps it from cracking. Liar, liar pants on fire. Well, I may have slightly overbaked it, which didn't help. But it wasn't at all dry, so I think that the recipe is flawed (it just couldn't be me!). I have made many pumpkin rolls before and I always have cracks (maybe it is me). I have friends who make perfect un-cracked rolls, but their cake is very rubbery and not pleasant to eat, so I'll stick with the cracks. I'm all about taste over appearance (which may explain some of the guys I've dated that my friends couldn't get at all. Or maybe I'm just weird).
One thing I would like to point out - the recipe calls for folding the egg whites into a yolk/chocolate mixture. A lot of people have problems with folding and end up with dense, rubbery sponge cakes. There are two things to do to avoid this. The first is to whisk in the first 1/4 to 1/3 of the whites into the batter until completely integrated, without worrying about deflating. This lightens the batter a little and makes it easier to fold in the remaining whites, which I do with a rubber spatula. The second thing to do it quit while you are ahead. By that, I mean don't worry about a few lighter streaks of batter. You can see by the photo that my batter isn't 100% homogenous. Some might argue that it won't bake up as attractively this way, and they may be right. However, it won't be heavy and dense either. Also, once the cake bakes the streaks generally are much less noticeable. I probably could have gone a couple strokes more here but erred on the safe side. The batter sat nice and high in my jellyroll pan so I was happy with it.
Rose has another annoying instruction in her recipe. When the cake comes out of the oven to cool, she has you sprinkle it with cocoa powder before laying a damp dishtowel over it. I know that the reason for this is to make sure the towel doesn't stick to the cake and pull out chunks when you remove it, but it seems that the main reason is to ensure that you won't ever be able to get your towel clean again. I think that it is unlikely that the towel will stick that much - next time I may try it without the cocoa powder, or just use the traditional powdered sugar (since you are rolling, filling and frosting it, the few white specks that might remain won't be noticed).
Once the cake has rested, you spread on the filling and roll it into a spiral. This was where the cussing occurred. The cake stuck a little bit to the greased and floured parchment (???), and it started to crack badly. I put the cake down, calmed myself, and used an offset icing spatula to gently loosen the entire cake from the parchment. I tried again from the other side, and it went a little better, but I still got cracks. However, I was very gentle in my rolling and managed to keep most of the filling inside of the cake, and it managed to maintain a spiral shape. I reasoned that the frosting on the outside would cover the flaws. Next I trimmed the ends because they were ragged, and cut off a 3 inch piece from one end on a diagonal, and set it on top of the log as the "knot."
I used a basic chocolate ganache (chocolate, cream and sour cream - the sour cream because I didn't have enough regular cream. It turned out pretty darn tasty) for the icing. Here is the roughed in icing. I set this in the refrigerator to firm up before adding the finishing touches.
Now on to the meringue mushrooms. Again, I followed instructions from The Cake Bible. I whipped the egg whites until frothy, then added cream of tartar and a little sugar (I think the tartaric acid helps the whites hold their shape and whip up higher, but you can omit it and still get good results). Rose calls for superfine sugar but I have trouble finding it here so I just used regular granulated. I use Domino sugar, which seems to be finer than other brands anyway, and it worked just fine. Once the whites held soft peaks, I added the rest of the sugar and beat to stiff peaks.
A lot of people have a hard time judging when something is at soft peaks or stiff peaks, so I thought I'd include a couple of photos. In each of these photos, I dipped the end of a whisk into the whites and pulled it out. You'll notice on the first photo (left) that the white drooped when I turned the whisk upright. The shape held but it slumped a little. If the peak disappears totally as you turn the whisk upright, then you aren't even at soft peaks yet. On the right, you can see that the peak held its shape and stayed in place as I rotated the whisk. One word of caution: it is possible to overbeat the whites and end up with a dry, useless product. It's best to err on the side of under-beating. If the whites start to lose their gloss, STOP! If you take them too far they will look curdled and will separate into ragged clumps. Properly beaten they are smooth and shiny. Since eggs are still relatively cheap, it's better to start over than to use over-beaten whites in a cake batter or souffle, where more expensive ingredients are just waiting to be ruined.
Once the whites were whipped, I put them in a piping bag with a 1/2 inch plain round tip and piped disks for the tops and little pyramids for the bases. I popped those into a low oven (200 degrees) for about an hour, or until I could just pull one off the silicone sheet without crushing the mushroom or having it fall apart (I always make extra because I ruin a few when testing.) A silicone baking sheet is the best thing to use because the meringues will stick to parchment or even a greased baking sheet. If you don't have a silicone sheet, I suggest using a plain, ungreased aluminum baking sheet and a thin metal spatula to help you remove them. You will probably lose a few, but you'll still get many usable pieces. My husband thought he had a better idea for the bases so you can see some cylinders on the right hand side (they didn't work). I left a little meringue in another piping bag with a small round tip to assemble the mushrooms. Here's how you do it. First you take a top and twist the tip of a sharp paring knife into the underside to make a small hole (be careful not to press hard or you'll come through the top). Basically you are scraping a hole rather than cutting one. Next, you pipe a drop of leftover meringue into the hole and insert a base. You set the mushroom back down on the baking sheet, tilting the cap of the mushroom if you like. Repeat with the remaining caps and bases. Return the meringues to the oven for another half hour or so, allowing the meringue "glue" to set and dry. Next you sieve some cocoa powder over them for the finishing touch. If you like you can turn them all over and sprinkle cocoa on the undersides as well (or if you want to be super cool, get an airbrush or paint brush and brush "gills" underneath. I'm not that cool).
As the meringues were drying, I put the finishing touches on the log. I used the tip of a small paring knife to make grooves for the bark, whipped up a quick American buttercream (butter, powdered sugar and a touch of milk with cocoa for color) and piped it in rounds on the "cut" pieces of log, then threw the mushrooms to it. I used too many mushrooms for it to be aesthetically pleasing, but what else was I going to do with them?
I thought that it all turned out pretty well for my first attempt. Of course, my experience with pumpkin rolls helped, but I was still pleasantly surprised at how well it looked (and tasted). It lasted about 15 minutes at the party I brought it to. Actually, it lasted about an hour because no one wanted to cut it. Then someone snuck in and got a piece of the top knot with a fork. Once people saw that it was no longer intact, they descended on it mercilessly.