1. Preheat the oven to 175°C. Line a 10-x-15-inch jelly roll pan with parchment paper.
2. Whisk the egg yolks and sugar by hand until lighter in colour, but not holding any air. Sift the cocoa powder over the yolks and whisk in.
3. In a separate bowl, whip the egg whites and salt on high speed until they hold a medium peak when the beaters are lifted. Fold a third of the whites into the yolk mixture using a whisk and then fold in the remaining two thirds until evenly incorporated. Spread the batter evenly into the prepared pan. Bake the cake for 25 minutes (it will rise up while baking and then fall once it is removed from the oven – that is OK) and let it cool completely in the pan.
4. For the cherries, simmer the cherries for about 15 minutes or until the juices are reduced by half, then add the sugar and simmer 5 minutes more. Remove the pot from the heat and stir in the kirsch. Cool and then chill the cherries until ready to assemble.
5. For the chocolate cream, bring the cream just to a simmer and pour it over the chocolate. Let this sit for 1 minute, then gently whisk until the chocolate has melted into the cream. Cool this too room temperature, then chill completely.
6. Whip the chocolate cream on medium speed until it holds a medium peak.
7. For assembly, whip the cream and skim milk powder until it holds a medium peak, then add the sugar.
8. Run a spatula around the outside edge of the cooled cake and turn it out onto a work surface dusted with icing sugar. Peel away the parchment paper and spread the whipped chocolate cream over the cake. Use a slotted spoon to spoon the cherries over the chocolate cream. Roll up the cake from the short side and carefully lift onto your serving platter so that the seam is at the bottom. Spread the whipped cream over the roulade to completely cover it and use a vegetable peeler to make chocolate curls to sprinkle on top. Chill until ready to serve.
9. The roulade can be made up to 8 hours before serving.