For a chocolate sponge cake, substitute 60 ml (1/4 cup) of flour with 60 ml (1/4 cup) of sifted cocoa powder.
You can temper the eggs (in their shells) by placing them in a bowl of hot water for 5 minutes.
The surface of the cake will be more even and the sides are less likely to collapse if the pan is not buttered.
When ready, the cake gives off a scrambled eggs aroma.
For a jelly roll
Line a 43 x 30-cm (17 x 12-inch) baking sheet (jelly roll pan with high edges) with parchment paper, letting it hang over two sides. Spread the sponge cake batter into the prepared pan and bake for about 12 minutes or until the cake is lightly browned. Sprinkle sugar on a sheet of parchment paper. Unmould the cake on the parchment paper and remove the backing that has baked with the cake. Roll the cake in the new parchment paper. Leave to cool. Unroll the cake and cover it with jam, buttercream, ganache, whipped cream, or other fillings. Roll the cake onto itself and sprinkle with icing sugar.