Chocolate Japanese Cake Roll

• ### Dry Ingredients
• 1/3 cup cake flour
• 1 1/2 TBSP cocoa powder
• 1/4 tsp baking soda
• 1/4 tsp cream of tartar
• scant 1/4 tsp fine salt
• ### Egg Yolk Mixture
• 3 egg yolks
• 1/4 cup sugar
• 2.5 TBSP oil (40ml)
• 1/4 tsp vanilla extract
• 3 TBSP milk (50ml)
• ### Meringue Mixture
• 4 egg whites
• 1/2 tsp cream of tartar
• 1/3 cup sugar
• ### Stabilized Whipped Cream
• 1 1/4 tsp powdered gelatin
• 5 tsp water
• 1 1/4 cup heavy cream
• 1 1/2 TBSP granulated sugar
• 2.5 TBSP cocoa powder, sifted
• pinch of salt
• 1/2 tsp vanilla extract

Instructions

1. 1

   Preheat the oven to 325°F (160°C). Grease lightly and line the bottom of a 9x13 inch (23x33 cm) baking pan with parchment.

2. 2

   When you separate your egg yolks and egg whites, please note that if an egg yolk breaks and gets into your whites, they will not whip up properly and the cake will not turn out well. For this reason, I suggest separating each egg over a small bowl and then transferring it to separate yolks and whites bowls. If an egg yolk happens to break and leak, do not use it. Reserve it for an omelet or another use.

3. 3

   Measuring the flour correctly is very important. Spoon the flour into the cup measure and shave off the excess flour with a butter knife without compressing it into the cup measure. Flour is very compactable, so if you simply scoop it out of the bag instead of spooning it in, you will end up with a lot more flour than needed and turn this delicate cake into a dense one. So do not skip this extra step.

4. 4

   Sift the flour, baking soda, cocoa powder, cream of tartar, and salt into a small bowl.

5. 5

   Beat the egg whites with a whisk attachment of your stand mixer on medium-high speed until frothy, about 2 minutes. Add cream of tartar and continue whipping until soft peaks form, about 3 minutes. Gradually add the sugar with the mixer running on medium speed. It's crucial to add the sugar slowly so the meringue forms properly; do so over a period of about 2 minutes. Beat until you reach medium stiff glossy peaks, around 3 minutes. Do not overbeat. When the meringue is overbeaten, it won't be smooth.

6. 6

   Whisk the egg yolks with sugar until thickened, for about 3–4 minutes. Pour in the oil and vanilla while whisking. Then add the milk and whisk to combine.

7. 7

   Sift the dry ingredients into the egg yolk mixture and gently fold them in until combined; don't overmix.

8. 8

   Gently fold 1/3 of the whipped egg whites into the egg yolks with a whisk—this will lighten the batter and make it easier to fold in the rest. Fold the remaining egg whites into the yolk mixture with a rubber spatula. Only fold until uniform in colour and combined; do not fold any more than necessary. Spread the batter evenly into the prepared pan.

9. 9

   Bake in the preheated oven for about 13–14.5 minutes. The cake should spring back in the center when gently pressed.

10. 10

    Remove from the oven and allow to cool for about 5 minutes. Run a butter knife around the edge between the cake and the baking pan. Invert the cake onto parchment paper placed on top of cooling racks. Gently remove the parchment that was on the bottom of the cake—this side will become the top of your roll. Allow the cake to cool on the racks for just about 5 minutes, but not much longer. Then invert it onto a clean piece of parchment paper and roll it into a roll, making sure the parchment is between the cake to prevent it from sticking. Allow it to cool completely in this shape (doing so will prevent it from cracking).

11. 11

    For the stabilized whipped cream, combine the gelatin and water and allow it to sit until thick, for about 5 minutes. Microwave the mixture until it dissolves and becomes liquid, about 10-second intervals. Allow this mixture to cool briefly, but not for too long, as we want it to remain in liquid form. Then add about 3 tbsp (45 ml) of your heavy cream to the mixture to ensure it remains very liquid. Add the remaining heavy cream, sugar, vanilla, and salt to the bowl of your mixer. Sift in the cocoa powder. Beat until thickened. Then while beating, pour in the gelatin mixture. Continue beating until medium-stiff peaks form.

12. 12

    Unroll your cooled cake. Spread the chocolate whipped cream over the cake.

13. 13

    Carefully roll up the cake. Wrap in plastic wrap and chill for at least 1½ hours in the fridge.