Line a baking sheet with parchment paper.

Combine the flour and cocoa and sift.

Separate the egg whites and yolks.

Preheat the oven to 190C (375F).

Lightly beat the egg whites.

Gradually add half of the sugar to the egg whites, mixing well after each addition.

Beat the egg whites until stiff peaks form.

In a separate bowl, combine the egg yolks and the remaining sugar.

Mix the egg yolks and sugar until light-colored and thick, achieving a mayonnaise-like consistency.

Pour the vegetable oil into the egg yolk mixture and mix well.

Add the hot water to the egg yolk mixture and mix.

Sift in the dry ingredients (flour and cocoa) and mix until just combined.

Gently fold in 1/3 of the beaten egg whites into the yolk mixture.

Fold in half of the remaining egg whites.

Add the yolk mixture to the remaining egg whites and fold in lightly with a rubber spatula, lifting the batter from the center.

Pour the batter into the prepared baking sheet.

Rap the baking sheet on the counter to remove air bubbles.

Bake at 190C (375F) for 15-17 minutes, or until a bamboo skewer inserted into the center comes out clean.

Let the cake cool on a cooling rack with the parchment paper attached.

Cover the cooled cake tightly with plastic wrap to prevent drying.

For the chocolate cream, melt the chocolate over a hot water bath.

In a separate bowl, add the sugar to the heavy cream and whip to very soft peaks.

Add 1/4 of the whipped cream to the melted chocolate and mix well.

Gradually add and mix in the remaining whipped heavy cream until it reaches the desired firmness.

Remove the parchment paper from the cooled cake and place it on a new sheet of parchment.

Diagonally cut off the edge of the cake that will be on the outside of the rolled cake.

Spread the chocolate cream evenly over the cake, leaving a 2-3 cm border on the cut end.

Lifting up the paper, slowly roll up the cake tightly.

Refrigerate the cake for at least 30 minutes before serving.