Leave eggs at room temperature. Melt butter and mix with vanilla oil. Chop chocolate finely. Preheat oven to 190℃.
Cut a sheet of baking paper to the size of the pan. Fold the 4 corners and staple to keep the shape.
I used a 30 cm x 22 cm pan.
Crack eggs in a bowl and beat with an electric beater.
Add sugar gradually as you mix and stir until it becomes a ribbon consistency.
The mixture should fall in a ribbon that swirls on top for a few seconds before sinking into the batter.
Sift cake flour and cocoa powder into the bowl and combine using a cutting motion with spatula.
Now pour in the butter while the mixture is still powdery, and mix using the same cutting motion. Pour in the batter into the middle of your baking pan.
Spread with a bench scraper and lightly tap on the kitchen counter a few times to release any air trapped inside. Bake in a preheated oven at 190℃ for about 8 minutes. Once it cools, cover with plastic wrap to prevent drying out.
Heat heavy cream in a sauce pan and when it is about to boil, remove from heat.
Melt chocolate in and combine, allowing the chocolate to melt from the heat of the cream.
Once the chocolate has melted completely, transfer to a mixing bowl. Mix with electric beater only until swirls have a smooth consistency.
Decide which way you will roll the cake and then cut diagonally about 1 cm off from the end edge. Spread half of the cream over the cake but leave 1 cm at the edge without cream.
Roll the cake as you separate from the baking paper and then wrap the rolled cake with the same paper. Now squeeze the roll and wrap with plastic wrap. Place in the fridge for a while.
Transfer the cake onto a tray and stabilize the shape. Spread and cover the remaining 3/4 cream over the cake with spatula.
Slice 1~2 cm off both ends. Then take a 5-6 cm diagonal slice from one side and place on top of the roll cake. Spread remaining cream to stabilize.
Using the back of a fork, drag lines all over the cake like a tree stump. Place in the fridge again for a while to rest and decorate.
Story Behind this Recipe
The recipe I always use is difficult to follow, so I modified the recipe for a beginner level baking class.
When you spread the batter evenly in the baking pan, try not to stir too much as it will make the cake less fluffy. You might find it takes time to whip the chocolate cream. However if you over whip, the cream hardens. So once the cream becomes an easy-to-spread consistency, it is okay. Decorate roughly, not neatly. it will look more natural.