8 ounces semisweet chocolate, chopped
4 tablespoons espresso or strong coffee
7 extra-large eggs, separated, the whites at room temperature
¾ cup sugar
Unsweetened cocoa powder, for dusting on the cake
1 recipe whipped cream (recipe follows)
Preheat the oven to 350 degrees F. Grease a 15x10-inch jelly roll pan. Line the pan with parchment paper and grease the paper.
In the top of a double boiler set over hot water, melt the chocolate with the espresso, stirring, until shiny and smooth. Remove the top of the double boiler and let the mixture cool slightly. In the bowl of a standing electric mixer fitted with the paddle attachment, beat the egg yolks with ½ cup of the sugar until thick and lemon colored. Scrape the slightly cooled chocolate mixture into the yolk mixture and combine well. Beat the egg whites with a handheld mixer until foamy. Gradually add the remaining ¼ cup sugar and beat but not dry peaks form. With a rubber spatula, fold the beaten whites in the chocolate cake base, mixing until no streaks of beaten whites show. Spread the batter in an even layer over the prepared pan and bake the sheet cake for 20 minutes. Remove the pan from the oven and immediately place a dampened clean kitchen towel over the sheet cake. Let cool completely at room temperature.
To assemble the roll: Remove the kitchen towel and dust the top of the sheet cake lightly with cocoa powder. Place a large piece of parchment paper on the work surface and invert the sheet cake onto it. Remove the piece of parchment on the top. With a long-bladed metal spatula, spread about half the whipped cream over the surface of the cake. Using the paper as an aid to roll up the sheet cake and starting with the long side nearest you, roll the cake into a long, relatively tight cylinder. (Do not exert too much pressure when you roll because the cake may bread o the buttercream will ooze out.) When you have finished rolling the log, place it, seam side down, on a baking sheet and refrigerate it, wrapped in parchment paper, until firm.
To serve, remove the parchment paper. With a serrated knife, trim the uneven, crusty ends of the log. With the spatula, frost the roll with the remaining whipped cream, starting with the top and covering the sides and ends evenly. With 2 long spatulas, carefully transfer the cake roll to a long cake platter. Serve. Store the cake, its cut end covered with plastic wrap, in the refrigerator for up to 1 day. Also great served alongside a bowl of fresh stawberries.
1 pint heavy cream
2 tablespoons granulated or confectioners’ sugar
1 teaspoon vanilla
Whip the heavy cream; add the confectioners or granulated sugar and vanilla and continue beating until cream holds soft peaks.