This is my own recipe composed from research I have done and meager experience. I lived in France over 6 years and ate many. In my opinion, it is the buttercream that makes or breaks this dessert, but there are also other crucial aspects such as the biscuit (or cake), how it is rolled and moistened with syrup. For convenience, we're going to call the cake a biscuit because that's what it's called in French.
The bûche de Noël is a complicated assembly of the following components:
- Biscuit
- Light, flavored syrup
- Buttercream filling and glazing
- Decorations (various, but especially mushrooms)
Here are the recipes for various components which will be needed roughly in reverse order for freshness and for having everything with which to build the dessert.
Meringue Mushrooms
These are the prinicpal decorations and are based on Swiss-style meringue.
| 4 | egg whites | |
| 250 g | powdered sugar (a bit more than a cup) |
1. Heat water up in a double boiler.
2. Separate out the egg whites into a 4-quart or bigger bowl.
3. Add the sugar and beat over the double boiler. If you are like me and don't have the physical endurance to beat 4 whites into stiff peaks by hand, do some beating over the double boiler and return to the mixer. Alternate back and forth until the meringue is accomplished.
4. Once the meringue is white and firm, continue to beat until cool. I cheat by rubbing the outsides of the bowl with ice cubes while the mixer is going at full tilt.
5. Heat the oven to 225°.
6. Spread a baking sheet with parchment paper. Fill a pastry bag with meringue and extrude disks and stems using either a large straight tip or the nozzle without tips. The challenge is to make these look like the heads and stems of common mushrooms. If some of the stems, which should start out thick, but get smaller as they go up, fall over, that's okay because you can apply them to the bûche as if growing out of its side and it actually looks quite realistic.
7. Bake (dry out) in the oven for about 1 hour. Remove and cool.
8. Carefully pick up the heads and, using the tip of a pointed knife, make a hole in the center of the bottom of each one. Glue the tip of a stem in each using a little bit of "royal glaze"—you can also use melted white chocolate if you have some on hand.
Royal Glaze
| 1 | egg white | |
| 6-12 tbsp | powdered sugar |
This glaze is made thick to be used as a glue. Just beat the egg white and the sugar together until a thick paste is obtained that is thinner than elementary school paste, but thicker than Elmer's Glue.
To simulate "dirt" on the mushrooms, plunge the head of each into baker's chocolate (powdered) and shake off the excess. Always be careful with the mushrooms because they are very fragile.
Buttercream
Use the recipe elsewhere on my web site. This is the challenging part of this dessert. The recipe as described produces much more than will be needed for 1 bûche. I would suggest cutting it to ¼, however, doing that makes it very hard to use a candy thermometer because the sauce pan will not have enough liquid in it to enable the candy thermometer to measure accurately. My advice is to plan on storing and using the buttercream in another application or make several of these logs at the same time. The full recipe is enough and then some to do 5 big logs (in which one full génoise recipe is used for the biscuit of each log. Sealed tightly in a container, buttercream keeps for a couple of weeks in the refrigerator and can even be frozen for longer periods. Basically, it keeps as long as butter.
The 4½ quart KitchenAid® (smallest model) is barely big enough to cope with this buttercream recipe. Most of the time, the whip will not be visible for how much mixture is in the bowl. When it comes time to put in the butter, you will need the two-piece spill shield to keep it from coming out all over the counter. Also, I use the same cooling trick I described for the meringue recipe above.
On buttercream... You will see on the Internet that the French usually make buttercream with the yolks instead of the whites. I have tried both. My opinion is that the whites work better. Certainly, according to current nutritional theory, they are healthier and I liked the texture, volume and flavor of the whites-based cream a lot better.
Light, Flavored Syrup
| ½ quart | water | |
| ¾ pound | sugar | |
| — | flavoring |
Bring water and sugar to a boil, then let them simmer for 2 minutes. After cooling, this syrup can be flavored using vanilla or almond extract, artificial rum flavoring, various alcohols, etc. For the bûche, we will want to flavor it with a garden variety rum flavoring from the grocery store. However, this can wait until we start to assemble the cake. I keep my syrup in a carafe, with plastic wrap over the opening, in the corner of my counter until I use it.
I have also used this same recipe to make the syrup for soaking a dessert named Baba au rhum except that in place of the flavoring, I used actual rum and then heated the syrup to 200° for about 5 minutes to chase away most of the alcohol leaving probably no more alcohol than remains in the syrup when vanilla or rum flavoring is used. The resulting syrup was immeasurably better.
The Biscuit
The biscuit consists of a very thin génoise cake—a simple sponge cake. This recipe makes enough for one big log such as the one pictured at top whose dimensions are roughly 12" long by 3" in diameter.
| 4 | whole eggs | |
| 120 g | sugar | |
| 120 g | white flour |
1. Heat water up in a double boiler.
2. Butter and flour a half-sheet baking pan. Preheat the oven to 350°. Set the baking pan in a cool place to keep the butter as hard as possible.
3. Beat the eggs and the sugar together over the double boiler until the mixture whitens and triples in volume. If you aren't strong enough to do this by hand, alternate between your mixer and the double boiler or use a hand-held mixer over the double boiler. This should take from 10 to 15 minutes by hand or 10 minutes "electrically." Continue beating until the mixture has cooled (use the ice cube trick described elsewhere on this page).
4. Fold the flour into the egg/sugar mixture on very low speed or by hand (in the manner of an angel food cake).
5. Pour the batter out onto the baking sheet and spread it uniformly over the whole pan or at least most of the pan. The goal is a very thin cake for rolling.
6. Bake for 15 minutes watching carefully that it doesn't brown around the edges. Any browning will result in crispy cake that won't be rollable. Cool the cake after removing it from the baking sheet using a spatula to disengage any part of it that have stuck. A terry cloth will provide a good cooling surface.
6bis. If the result is too dried out or over-baked to roll up easily, then you screwed up and need to start over.
7. Cut a clean rectangle as big as you desire from this cake. You are now ready to assemble the bûche.
Assembly
1. Brush the top side of the biscuit liberally with the flavored syrup. Don't be afraid to soak it, especially if it is a little hard. Turn it over and do the bottom.
2. Coat the biscuit with at least one-eighth of an inch of buttercream. This can be flavored with almond which will contrast and complement the rum. Or, it can be reinforced with chocolate. To do this, melt together your favorite molding or dipping chocolates and beat into buttercream. I use almond-flavored white buttercream for the inside of the log and chocolate-reinforced for the outside. As will be shown, I also use the white for the ends of the log.
3. Carefully roll the biscuit as tightly as the buttercream will allow (don't squirt it all out the ends). Brush more syrup on the cake part as it is rolled (don't drip it on the buttercream).
4. Cut off the ends cleanly. Cut the biscuit almost to desired length, then cut the ends at a diagonal saving a wedge-shaped piece to use on top to simulate a snipped branch. Glue that piece in place using a bit of buttercream.
5. Using some of the buttercream set aside for this purpose which is white, lighter, flavored with white chocolate, etc., face the cut ends of the log including the cut branch. Using melted chocolate in a squeeze bottle or some other trick, style growth rings by applying a swirl or concentric circles on these faces.
6. Using buttercream you have bolstered with dark chocolate, thickly ice the remaining surfaces of the biscuit taking care to build up to, but not ruin, the cut faces you have made. Use a fork to sculpt tree bark into the log. If you are working in a hot kitchen, you may want to put the buttercream in the refrigerator before and after some of these assembly steps.
Trick: If the buttercream ever looks curdled, beat it vigorously over a double boiler with a whisk taking care not to melt it any more than necessary to eliminate the curds. Then place the buttercream back in the refrigerator. Successful decorating is a matter of having the buttercream warm and pliable enough to spread and yet cold and hard enough to shape and not slip off or become a mess to use.
7. Place the log onto its final serving plate if you haven't already done this. The plate can be predecorated with doilies and squirts of chocolate or fruit coulée. Once in place, apply the mushrooms into the buttercream. Warning: If the buttercream is too cold, the mushrooms will be broken during application. Sprinkle powdered sugar and powdered baker's chocolate over the whole plate and log. "Leaves" cut from marzipan, fruit-shaped gum drops, etc. and, in general, just about any possible decor can be included before or after the sprinkling.