Chocolate Roll Cake

The Art.

    It's Christmas baking time, everybody! I've posted quite a few Christmas cookies over the years, including Iced Snowflake Sugar Cookies, Gingerbread Cookies, and a Meringue Christmas Tree. This year, I wanted to step away from the cookies and make a pretty Christmas cake. The idea of making an iced yule log was appealing, but by now everyone has eaten so many sweets they didn't even want to think about icing. So, I settled on this simple Chocolate Roll Cake. A naked dark chocolate sponge filled with barely sweetened whipped cream is the perfect treat for everyone who's had a few too many of Santa's cookies...but still has room for a little more.

The Science.

    The trickiest part of making a roll cake is getting a beautiful swirl shape without any splits or cracks. There are several factors that contribute to success here. First, this cake is a flourless sponge with lots of whipped egg whites that make the cake very elastic and easy to handle. Second, baking the cake on a silicone mat not only prevents the bottom from getting overbaked and dry, but also helps immensely with the rolling process because you can use the mat for support as you roll. And finally, rolling the cake up while it's warm and cooling it in this shape makes a beautiful round roll that won't look squashed in the end.

The Recipe.

Flourless Chocolate Sponge:
6 egg whites, at room temperature
1/4 teaspoon cream of tartar
3/4 cup sugar, divided
6 egg yolks
1/3 cup dark cocoa powder

Preheat oven to 350°F and line a 10in by 15in jelly roll pan with a silicone mat. Whip the egg whites and cream of tartar on medium-high speed until soft peaks form. Gradually add half the sugar while beating, until stiff peaks form. Set aside. In another bowl, combine the remaining sugar, egg yolks, and cocoa powder. Beat on medium-high speed for at least two minutes, making sure to scrape the bowl periodically. Getting this mixture well mixed and fluffy is very important for the texture of the cake. Add 1/4 of the egg whites to the chocolate mixture and stir to lighten the batter. Gently fold in the rest of the egg whites just until combined, making sure not to deflate the batter while doing so. Pour batter onto prepared pan with mat, spreading the top very evenly with a spatula. Bake for 15 minutes, until the center springs back when lightly touched with your fingertip. Cool in the pan for 10 minutes, then run a sharpe knife along the edges to release them from the pan. While the cake is still warm, dust the top with a small amount of cocoa and cover the top with parchment paper (the cocoa prevents sticking). Begin rolling up the warm cake from the short side, rolling up the parchment paper and the silicone mat right along with the cake. Once the cake is rolled, place it on the countertop with the outside edge on the bottom. Support the long sides of the cake with a rolling pin, baking pan, storage jar, or any other long object you have in your kitchen, in order to prevent the roll from sagging while it cools. Meanwhile, make the whipped cream.

Stabilized Whipped Cream:
1 teaspoon gelatin
3 tablespoons boiling water
1 cup heavy whipping cream, chilled
1/4 cup powdered sugar

    Place a metal mixing bowl and metal whisk attachment in the freezer for 15 minutes. Meanwhile, combine gelatin and boiling water in a small bowl and stir until dissolved. Gradually stir whipping cream into the gelatin, going slowly so the gelatin doesn't seize. Place whipping cream and gelatin in the refrigerator for 10 minutes. Whip the cream/gelatin in the chilled bowl with the chilled whisk on medium speed until soft peaks form. Continue beating while gradually adding the powdered sugar, until stiff peaks form. Refrigerate cream until the cake is completely cool.

Assembly:

    Gently unroll the cake and remove the parchment paper from the top, leaving the cake on the silicone mat. Lightly brush away any excess cocoa powder. Spread the whipped cream evenly over the top of the cake, leaving one inch bare on all the edges. Begin rolling up the cake from the short end, the same direction you rolled it before. As you start rolling, gently pull the silicone mat up and away from the cake with one hand as you form a tight cake roll with the other. Using the mat in this way supports the cake and helps you roll it more tightly. You want to roll the cake so that there are no air holes and the center has a nice swirl, but not so tight that you tear the cake. Going slowly and keeping the mat taught will make this easier.
    Once the cake is rolled, place it with the outside edge down on a cake board or serving dish. Cover
with parchment paper and support the long sides once again to keep a round shape. Refrigerate for at least four hours. Before serving, remove the parchment paper and trim off the short ends of the cake (approximately 1/2 inch) with a sharp serrated knife to reveal a beautiful swirl filled with cream. You may arrange the cake board with any decorations you wish; I chose rosemary sprigs, sugared cranberries, and star anise for a rustic Christmas theme. You can also skip the decorations and use a sifter to dust the cake with either powdered sugar or cocoa for a simpler look. Leftover cake can be stored in the refrigerator in an airtight container for up to three days.