Instructions:

1. Preheat your oven to 350°F (180°C). Grease and line a baking sheet with parchment paper, ensuring it extends slightly beyond the edges.
2. In a bowl, sift together cake flour, cocoa powder, and cornstarch. Set aside.
3. In a large mixing bowl, beat the eggs and granulated sugar on high speed until the mixture is pale, fluffy, and almost doubled in volume. This may take about 5-7 minutes.
4. Gently fold the sifted dry ingredients into the egg mixture in three parts, ensuring a smooth and consistent batter.
5. Pour the batter onto the prepared baking sheet, spreading it evenly with an offset spatula.
6. Bake in the preheated oven for approximately 12-15 minutes or until the cake is set and springs back lightly when touched.
7. While the cake is baking, lay a clean kitchen towel on a flat surface and dust it lightly with cocoa powder.
8. Once baked, immediately invert the cake onto the prepared towel. Peel off the parchment paper and roll the cake gently, starting from the short end, with the towel inside. Allow it to cool completely.
9. Prepare your favorite filling, such as whipped cream or ganache.
10. Carefully unroll the cooled cake, spread the filling evenly, and re-roll the cake without the towel.
11. Refrigerate the Chocolate Swiss Roll for at least an hour before slicing and serving. Enjoy the heavenly combination of soft cake and luscious chocolate filling!