Chocolate Japanese Cake Roll

Directions

• Preheat the oven to 325F. Grease lightly and line the bottom of a 9x13 baking pan with parchment.
• When you separate your egg yolks and egg whites, please note, that if your egg yolk breaks and makes it into your whites - they will not whip up properly and the cake will not turn out. For this reason, I suggest separating each egg over a small bowl then transferring it to separate yolks and whites bowls. If your egg yolk happens to break and leak - do not use it. Reserve it for an omelet or another use.
• 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 and not spoon it in, you will end up getting a lot more flour than needed and turning this delicate cake into a dense one. So do not skip this extra step.
• Sift flour, baking soda, cocoa powder, cream of tartar and salt into a small bowl.
• Beat 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 for the meringue to properly form, do so for a period of about 2 minutes. Beat until you reach medium stiff glossy peaks, around 3 minutes. Do not overbeat. When this is overbeat, your meringue won't be smooth.
• Whisk egg yolks with sugar until thickened, for about 3-4 minutes. Pour in the oil and vanilla while whisking. Then add milk and whisk to combine.
• Sift the dry ingredients into the egg yolk mixture and gently fold them in until combined; don't overmix.
• 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 in the rest of the 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.
• Bake in preheated oven for about 13-14.5 minutes. The cake should spring back in the center when gently pressed.
• Remove from the oven and allow to cool for about 5 minutes. Run a butter knife around between the cake and the baking pan. Invert the cake into a parchment paper placed on top of cooling racks. Gently remove the parchment that used to be on the bottom of the cake - this side will become the top of your roll. Allow the cake to cool on racks for just about 5 minutes, but not much more. Then invert it on a clean piece of parchment paper and roll it into a roll, making sure the parchment is in between the cake, to prevent it from sticking. Allow it to cool completely in this shape (doing so will prevent it from cracking.)
• For the stabilized whipped cream, combine 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 in liquid shape. Then add about 3 TBSPs 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 gelatin mixture. Continue beating until medium-stiff peaks form.
• Unroll your cooled caked. Spread chocolate whipped cream over the cake.
• Carefully roll up the cake. Wrap in plastic wrap and chill for at least 1 ½ hours in the fridge.