Preheat the oven to 375˚F. Combine in a large roasting pan:
1 celery root, trimmed, peeled, and cut into large chunks
2 russet potatoes (...
Since this is such a doozie of a recipe, I'll get right to the point. Making a yule log cake is a process, but sometimes nothing else will do. It's completely over the top, classic, and just a little cheesy. It's also delicious.
I highly recommend making this over a span of 2 days unless you have the better part of a day to futz around in the kitchen. It's very easy to make the cake and the filling on day one, then freeze the cake and make the icing and meringue mushrooms on day two. And yes, you absolutely have to make the mushrooms. It seems like kind of a pain when you're doing it, but they're seriously easy to make and really adorable.
A few notes on technique.
· Sometimes roll cake recipes have you roll the cake up in a kitchen towel while it cools. That is not necessary here. This sponge cake is really moist, and I had no trouble with cracking when I rolled it up.
· When inverting the cake onto the aluminum foil after baking, be brave! Just flip the pan quickly and confidently. It will all be fine.
· Often, yule log cakes are filled with chocolate or coffee-flavored buttercream. I've done that before and found it overwhelmingly rich and sweet. It was kind of sickening in a way. So this year I opted to fill the cake with a thin layer of raspberry jam for acidity and a layer of lightly flavored whipped cream. It makes for a much lighter and less sweet cake, which appeals more to my palate. That said, if you love buttercream, you can use your favorite recipe to fill the cake.
· The whipped cream filling is stabilized with gelatin to help the cream hold up longer. It's a cool pastry technique that will allow you some wiggle room as to when you serve the cake. The filled cake can also be frozen for quite a while before serving.
· If the chocolate icing seizes up after you add the cream, don't panic. Dump it into a blender and blend until smooth, then add the powdered sugar.
· If you don't already have a small offset spatula, I recommend buying one. They're incredibly handy little tools. I use mine almost daily for both pastry and non-pastry tasks. I find them much more maneuverable than the large offset spatulas.
Other showstopping desserts you might enjoy: Quick Cocoa Cake, Flourless Chocolate Decadence, Buttermilk Layer Cake With Bittersweet Chocolate Frosting and Coconut
First, prepare the sponge cake sheet:
Preheat the oven to 400°F. Grease an 18 x 12-inch rimmed baking sheet (also known as a half sheet pan) and line the bottom with parchment.
Sift together and return to the sifter:
3/4 cup cake flour
1 teaspoon baking powder
1/4 teaspoon salt
Heat in a small saucepan until the butter is melted and the milk is steaming slightly:
1/4 cup milk
3 tablespoons butter
Remove from the heat while the eggs whip.
Combine in the bowl of a stand mixer:
3/4 cup sugar
5 large eggs
Beat, using the whisk attachment, until light-colored, tripled in volume, and the consistency of softly whipped cream (if using a hand mixer, this will take about 10 minutes). Sift the flour mixture over the whipped eggs in 3 additions, folding in after each addition. Add the hot milk mixture all at once and fold in until combined. Scrape the batter into the pan and spread into an even layer.
Bake until the top is golden brown and springs back when lightly pressed, 8 to 10 minutes. While the cake is still hot, run a knife along the edges to release it from the pan. Immediately invert the cake onto a sheet of aluminum foil on top of a sheet pan or cutting board and remove the pan. Let the cake cool completely before peeling off the parchment.
Peel off the parchment. Have a fresh parchment sheet on your work surface and invert the cake, foil and all, onto the parchment so that the cake is right side up. Peel off the foil, removing the brown "skin" from the cake as you do so.
Prepare the filling:
Pour into a small heatproof cup:
1 1/2 tablespoons cold water
Sprinkle over the top of the water:
3/4 teaspoon unflavored gelatin
Let the gelatin soften for 5 minutes, then place the cup in a pan of simmering water until the gelatin is melted and clear. Let cool to room temperature.
Beat in the chilled bowl of a stand mixer fitted with the whisk attachment at medium-high speed until thickened:
1 1/2 cups cold heavy cream
2 tablespoons sugar
1/2 teaspoon vanilla
(2 teaspoons instant coffee or espresso powder)
(If you would like to flavor the whipped cream with chocolate, whisk 3 tablespoons cocoa powder into a small amount of the cream, then add to the remaining cream in the bowl.) With the mixer running, slowly pour the gelatin into the cream. Beat to the desired consistency. For this application, the cream should be stiff but not grainy.
Assemble the cake:
Spread the sponge cake roll with:
3/4 cup raspberry jam
Spread the whipped cream over the jam in an even layer, going to within 1/2-inch of the edges of the cake. Starting with a short edge and using the parchment to help roll, roll up the cake tightly, as if you were rolling a sleeping bag. Wrap the rolled up cake in the parchment, using a small piece of tape to hold it in place. For easiest handling, freeze for at least 3 hours until semi-frozen. It will keep frozen for up to 3 months.
Prepare the meringue mushrooms:
While the cake freezes, prepare the mushrooms. Preheat the oven to 200°F. Line 2 baking sheets with parchment.
Whisk together in a heatproof bowl or the top of a double boiler (I just used the bowl of my stand mixer):
4 large egg whites (about 1/2 cup)
1 cup superfine or granulated sugar
1 teaspoon vanilla
1/2 teaspoon cream of tartar
Set the bowl in a skillet or over a pot of gently simmering water and whisk until the whites are warm, not hot, to the touch (110°F to 115°F). Remove the bowl from the skillet and beat on high speed until the whites are stiff and glossy.
Scrape the meringue into a pastry bag fitted with a 1/2-inch plain tip. Pipe thin pointed kiss shapes about 1" tall to make stems. Pipe round button shapes to make mushroom caps. Moisten your finger with water to smooth the caps if necessary. Dust lightly with:
Bake until crisp and completely dry, about 2 hours. Let cool in the turned off oven. Melt:
2 ounces semisweet or bittersweet chocolate, chopped
Use a sharp knife to cut off and discard the pointed ends of the meringue stems. Spread a little melted chocolate on the flat side of each mushroom cap and attach the stems before the chocolate sets. Let stand until the chocolate is set. The mushrooms can be stored in an airtight container for up to 4 weeks (if it's not humid).
Prepare the frosting:
Melt in the top of a double boiler:
6 ounces unsweetened chocolate, chopped
6 tablespoons butter, cut into small pieces
Heat in a small saucepan until steaming:
1/2 cup heavy cream
1 tablespoon espresso powder
Whisk the heavy cream into the melted chocolate. Gradually add, beating until spreadable:
4 cups confectioner's sugar, sifted
If the icing is still too runny, refrigerate it, checking every 5 minutes or so, until thickened. Use immediately.
Frost and decorate the cake:
Using an offset spatula, spread the icing over the cake, leaving the ends bare. Use a sharp knife dipped in hot water and dried to cut a 2-inch slice from one end of the cake. Set the cake roll on a serving plate. Place the reserved slice on either side of the cake to resemble a stump, and use some of the icing to cover the joints. Drag the tines of a fork through the icing to mimic the appearance of bark. If serving immediately, decorate with the meringue mushrooms. Otherwise, refrigerate the cake, covered, until 30 minutes before you plan to serve it, and decorate with the mushrooms just before serving. If desired, you may also dust the cake with powdered sugar to mimic snow. To serve, cut off slices with a sharp knife that has been dipped in hot water and dried off between each slice.