Instructions

Making the Cake Batter (45 minutes)

1. Lightly butter the base and sides of a 9×13-inch rimmed cookie sheet or jelly roll pan and line with parchment paper.  Preheat the oven to 350 F.
2. Place the chocolate in a stainless steel bowl set over a saucepan of gently simmering water.  Stir constantly until the chocolate is fully melted, then remove from the heat and set aside to cool.
3. Separate the eggs, placing the whites and yolks in separate large mixing bowls.
4. Beat the egg whites with a handheld electric mixer until stiff peaks form.  The mixture should not fall out of the bowl when it’s turned upside down.
5. In a large, clean bowl, beat the egg yolks and caster sugar together with a handheld electric mixer.  The mixture should be increase in volume and be pale in color.  When the whisk is lifted, the mixture should fall in a thick ribbon that holds its shape for a couple seconds before sinking back into the mix.
6. Gently fold the melted and cooled chocolate into the egg yolk and sugar mixture, making sure they are fully mixed.
7. Put two large spoonfuls of beaten egg whites into the chocolate mixture and stir it in carefully to slacken the mixture, then fold in the remaining egg whites until no white flecks remain.
8. Sift in the cocoa powder and fold it in, being careful not to knock the air out of the batter.
9. Gently pour the batter into the prepared pan, tilting the pan to move the batter into the corners.  Make sure the batter is level.

Baking the Cake (20 minutes + 1-2 hours cooling)

1. Bake the cake at 350 for 20-25 minutes, until the cake is well risen and the top feels a little crisp.  Be careful not to overbake.
2. Put the cake on a wire rack and let it cool completely in the pan.

Rolling & Decorating the Cake (15 minutes)

1. Put a large sheet of parchment paper on a big cutting board and sift a little icing sugar all over the paper.
2. Pour the heavy whipping cream into a medium mixing bowl and beat with a handheld electric mixer until the cream forms fairly stiff peaks, but is not dry.  Check out my article here on whipping cream.
3. Turn the cake out onto the sugar-dusted parchment paper and carefully peel off the paper.
4. Spread the whipped cream evenly onto the cake.  Make sure to leave 1 inch uncovered all the way around the cake.
5. Turn the cutting board so a short side of the cake is facing you.  Using a sharp knife, cut almost all the way through the cake about an inch in from the short end.  Start the roll by pushing this little strip over, then roll up the rest of the cake as tightly as you can.  Use the parchment paper to help.  It will crack as it’s rolled.
6. Trim the ends with a sharp serrated knife, then dust the cake with more icing sugar if desired.  Transfer it to the serving platter with a large cake spatula.  Serve within a few hours.