If you've been reading this blog for very long, then you know I love a cake roll. I found this recipe in a secondhand baking textbook, and was instantly smitten. The alternating chocolate ganache and vanilla buttercream interior was so striking on the page, I had to try my hand at the technique.
Below you'll find a pictoral of the Harlequin buttercream filling process. I think the finished cake looks quite daunting, but once you see how it's made, you may be inspired to try it! It's easier than it looks.
This last process shot is my favorite. I had anticipated having a real mess on my hands after rolling up the cake, but it was a relatively tidy affair. It's important that the buttercream isn't too lax in texture. It should have a little heft to it so it rolls up nice and clean.
One prerequisite for this recipe - you must like buttercream (no issues here!). This cake is rich, so a small slice goes a long way. The textbook suggests using slices of this cake to create a beautiful dessert tray. I can imagine slices fanned out on a fancy platter would be quite pretty.
Harlequin Truffle Cake Roll
Source: Professional Baking textbook with my adaptations and notes
Yields 12 servings
1/3 cup/3.5 ounces heavy cream
5 ounces dark chocolate, chopped
1 1/2 cups/340 g unsalted butter, softened
4 cups/510 g confectioners’ sugar
1 teaspoon vanilla extract
Pinch of salt
2 tablespoons unsweet dark cocoa powder
In a saucepan, bring the cream to a simmer. Remove from the heat and pour in the chopped chocolate. Whisk to combine. Transfer the mixture to a shallow dish and transfer to the refrigerator. Stir the mixture intermittently to speed cooling.
In a large bowl beat the butter until creamy. Add the confectioners’ sugar and beat until light and fluffy, about 4 minutes. Beat in the vanilla extract and pinch of salt.
Remove half of the frosting and place it in a piping bag fitted with a 1/2-inch decorator tip (or no tip, and a 1/2-inch hole cut in the end). Beat the cooled chocolate mixture and 2 tablespoons dark cocoa into the remaining frosting. Transfer the chocolate frosting to a piping bag fitted with 1/2-inch decorator tip (or no tip, and a 1/2-inch hole cut as previously mentioned). Set aside. Keep the bags at room temperature.
1/2 cup egg yolks (about 7 yolks from large eggs)
3 tablespoons/ 1 1/2 ounces granulated sugar
1 tablespoon vegetable oil
1/3 cup/2 ounces cake flour, sifted
1/4 cup egg whites (about 2 egg whites from large eggs)
Confectioners’ sugar for dusting
Beat the egg yolks and sugar together in a standing mixer on high speed until light in color, about 5-8 minutes. Gradually add in the oil. You can tell the mixture is properly whipped when it has the appearance of lemon pudding.
Gently fold in the cake flour using a large rubber spatula. Set aside.
Beat the egg whites in a separate bowl until soft peaks form. Gently fold the beaten egg whites into the yolk mixture.
Preheat the oven to 350°F. Grease a 10x 15-inch baking sheet with vegetables shortening and line it with parchment paper (the greased surface helps the paper to stick to the pan). Carefully spread the mixture in an even layer over the parchment with an offset spatula.
Bake for 8 to 10 minutes, or until the cake just starts to brown around the edges. The cake may look glossy and underdone in the middle, but looks can be deceiving. Check the cake’s center by pressing your finger on the cake. If it springs back, it’s done. Be careful not to over-bake this cake, or it break into pieces as you try to roll it.
Let the cake cool slightly. Run a knife around the edge of the pan and turn the cake onto a work surface dusted with powdered sugar (put a piece of waxed paper down first and clean-up will be a snap). Peel off the parchment paper. Trim the brown edges away from the cake. Let the cake cool completely.
Pipe spaced lines of chocolate frosting across the length of the cake. Leave just enough space to allow for same-sized lines of white icing between the chocolate icing. Pipe the white frosting between the chocolate rows, filling the gaps completely. You should have leftover chocolate frosting, reserve it for later use. Gently begin to roll the cake, starting at a long side, pushing it forward with your fingers. Roll the cake up completely and wipe away any excess frosting that gets squished out during rolling. Place the cake roll on a large sheet of waxed paper (or parchment) and roll the cake up into the paper. Chill the cake in the freezer until firm.
Chocolate glaze and topping
4 oz. chocolate, finely chopped
1/2 cup/120 g heavy cream
Assorted chocolate bonbons
Place heavy cream in a large microwaveable bowl. Heat in the microwave at 40 second intervals until very hot but not boiling (you can do this on the stove top if you don’t have a microwave). Stir in chopped chocolate. Let stand for 3 minutes then begin gently stirring mixture. You can use a whisk, but do not whisk vigorously as it will create air bubbles in the finished glaze.
Remove cake from freezer and place it on a grid baking rack; place the rack on top of a large baking pan. Pour glaze over entire surface, allowing the excess to drip into the pan. Let stand for 2 minutes, and then transfer the cake to the freezer.
Transfer the remaining chocolate frosting to a piping bag fitted with a large open star tip. Pipe an undulating line of frosting on top of the cake. Garnish with chocolate bonbons. Cut the cake into pieces with a warmed knife, cleaning between slices, while it is still cold. Let the slices come to room temperature before serving.